Syllabus - Queens College Academic Senate - CUNY
Syllabus - Queens College Academic Senate - CUNY
Syllabus - Queens College Academic Senate - CUNY
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CHEMISTRY 113.1<br />
INTRODUCTION TO CHEMICAL TECHNIQUES<br />
Fall 2008<br />
SECTION 1. INSTRUCTOR AND COURSE INFORMATION<br />
Instructor: Ms. Luxi Li<br />
Office: Remsen 017<br />
Office hours: Wednesday, 1:00 - 2:00 pm<br />
Telephone: (718) 997-4182<br />
E-mail: luxi.li@qc.cuny.edu<br />
Laboratory: Tuesday, 1:40 – 4:30 PM; Remsen 209<br />
Course<br />
Content: An introductory laboratory course in basic chemistry techniques.<br />
Goals/<br />
Objectives: Discovery of basic chemical principles and an introduction to basic chemical<br />
techniques through experimentation. Introduction to data collection, recording,<br />
analysis, evaluation and reporting.<br />
Webpage: http://chem.qc.cuny.edu/~introchemlab/CHEM113/home.html<br />
Required<br />
Text: <strong>Queens</strong> <strong>College</strong> Chemistry 113.1 Laboratory Manual.<br />
SECTION 2. POLICIES/RULES<br />
Attendance: Attendance in laboratory is mandatory. An unexcused absence results in the loss of<br />
all points associated with that laboratory (i.e., 15 pts: prelaboratory quiz, laboratory<br />
project grade). If you have a university excused absence (such as illness, etc), you<br />
must show the excuse to the laboratory instructor the week after the absence. If you<br />
will miss a laboratory due to religious observance, you must inform the<br />
instructor the week BEFORE the absence, or the absence will not be excused.<br />
If the absence is excused, there will be a make-up laboratory (including quiz). This<br />
make-up laboratory will be administered after the laboratory practical during the 14 th<br />
week.<br />
Tardiness: It is your responsibility to attend class and to be punctual. Pre-laboratory quizzes<br />
will be given at the beginning of class and students will be given exactly 30 minutes<br />
to complete the quiz. Tardiness will not result in additional time being given for prelaboratory<br />
quizzes.
Laboratories: There are 14 laboratories, including the check-in/introductory laboratory and the<br />
final examination meeting. The grade will be determined from pre-laboratory<br />
quizzes, laboratory techniques, laboratory reports, and laboratory practical.<br />
Pre-laboratory<br />
quizzes: All pre-laboratory quizzes will be 30 minutes in length and will be given at the<br />
beginning of the laboratory period. Additional time will not be given to students<br />
who are tardy. These quizzes will consist of three questions, which may contain<br />
multiple parts:<br />
Question 1. A post-laboratory question from the previous experiment.<br />
Question 2. A safety question about the current experiment.<br />
Question 3. A pre-laboratory question from the current experiment.<br />
Laboratory<br />
project: A complete laboratory project consists of the following documents, which should<br />
be stapled together in the order listed:<br />
1. Hard copy of the laboratory report<br />
2. The pre-laboratory questions<br />
3. The laboratory report sheet<br />
4. The post laboratory questions<br />
In addition to this package, an electronic version of the laboratory report should also<br />
be submitted to Blackboard. The completed project (i.e., Items 1-4) must be<br />
submitted at the beginning of the laboratory period on the date due (see the<br />
schedule). An electronic version (i.e., Word or WordPerfect) of the laboratory report<br />
must be submitted to Blackboard on the date due. Electronic versions of<br />
laboratory reports will be submitted to Turn-it-in software and checked for<br />
plagiarism. Turn-it-in checks both internet sources and previously submitted<br />
reports. Failure to submit an electronic version of the report will result in a zero on<br />
the laboratory report.<br />
Laboratory<br />
worksheets: Some laboratories do not have projects associated with them. For these laboratories,<br />
the worksheet that accompanies the laboratory must be submitted at the end of the<br />
laboratory in question.<br />
Laboratory<br />
reports: A style guide for the laboratory reports is attached to this document and can also be<br />
found on the course website. Unless specified by the laboratory instructor, laboratory<br />
reports are limited in length to 6 pages, excluding Figures and Tables.<br />
<strong>Academic</strong><br />
dishonesty: While it is natural to discuss experiments among each other, copying and/or<br />
plagiarism will NOT be tolerated on any assignment and will be treated in<br />
accordance with university policy. This policy can be found at:<br />
http://www1.cuny.edu/portal_ur/content/2004/policies/image/policy.pdf<br />
Electronic versions of laboratory reports will be submitted to Turn-it-in
SECTION 3. GRADING<br />
software and checked for plagiarism. Turn-it-in checks both internet sources<br />
and previously submitted reports. We should note here that copying and<br />
downloading graphs from the internet, without express permission of the instructor,<br />
constitutes plagiarism (even if referenced). An originality score $ 30% (indicating<br />
that # 70% of the work is original) from a single reference will result in a grade<br />
of zero on the laboratory report in question.<br />
Course<br />
grading: Pre-laboratory quizzes (12 @ 10 pts) 120 pts<br />
Laboratory Projects (12 @ 20 pts) 240 pts<br />
Laboratory practical 60 pts<br />
Total: 420 pts<br />
Grading for<br />
Project: 1. Laboratory report *<br />
a. Style guide formatting (0.5 pt)<br />
b. Introduction and Experiment (1.5 pt)<br />
d. Results and Discussion (2 pts)<br />
7 pt<br />
2. Pre-laboratory questions 4 pt<br />
3. Report sheet 3 pt<br />
4. Post laboratory questions 4 pt<br />
Safety and laboratory technique 2 pt<br />
*<br />
Failure to submit an electronic version of the laboratory report will result in the loss of these 7<br />
points.
Laboratory Schedule<br />
Lab Pre-Lab (60 min) Lab Work (120 min) Projects due<br />
1 <strong>Syllabus</strong> and safety.<br />
Safety exam.<br />
2 Pre-laboratory quiz<br />
Density and graphing.<br />
3 Pre-laboratory quiz<br />
Chemical formulas.<br />
4 Pre-laboratory quiz<br />
Moles.<br />
5 Pre-laboratory quiz<br />
Chemical reactions.<br />
6 Pre-laboratory quiz<br />
Acid/base chemistry<br />
7 Pre-laboratory quiz<br />
Acid/base chemistry<br />
8 Pre-laboratory quiz<br />
Energy in chemistry.<br />
9 Pre-laboratory quiz<br />
Metal reactivity.<br />
10 Pre-laboratory quiz<br />
Electronic spectroscopy<br />
11 Pre-laboratory quiz<br />
Redox Chemistry<br />
12 Chemical kinetics<br />
(60 min lecture)<br />
Check-in.<br />
Laboratory techniques.<br />
Finish laboratory techniques.<br />
Density<br />
Laboratory Techniques<br />
Project.<br />
Law of definite proportions. Density Project<br />
Stoichiometry. Law of definite<br />
proportions project.<br />
Copper reactions Stoichiometry project.<br />
Acid/base titrations with an<br />
indicator<br />
13 Pre-laboratory quiz<br />
Finish Kinetics of bleaching experiment<br />
Kinetics data analysis using computers (in recitation room)<br />
14 Laboratory check-out and<br />
LABORATORY PRACTICAL (60 pts).<br />
Copper reaction project.<br />
Potentiometric analysis. Acid/base project 1.<br />
Heat of reactions. Acid/base project 2.<br />
Activity of metals. Heat of reaction project.<br />
Emission and Beer’s Law. Activity of metal project.<br />
Redox titration of bleach Beer’s Law Project<br />
Kinetics of bleaching Redox Titration Project<br />
Kinetics Project.
Laboratory Drawer Combination:<br />
Chemistry 113.1.<br />
Introduction to Chemical Techniques<br />
Laboratory Manual<br />
Cherice M. Evans, Fred H. Watson and<br />
Gary L. Findley
Contents<br />
Section 1. General Rules 1<br />
Section 2. Schedule 5<br />
Section 3. Laboratory Safety 7<br />
Section 4. Freshman Chemistry Style Guide 21<br />
Section 5. Instructions for Turn-it-in Assignments 33<br />
Section 6. Useful information 37<br />
Experiment 1. Check-in and Basic Laboratory Techniques 39<br />
Experiment 2. Density 59<br />
Experiment 3. The Law of Definite Proportions 75<br />
Experiment 4. Stoichiometry of a Reaction 93<br />
Experiment 5. Copper reactions 105<br />
ii
QC Chemistry Laboratory Manual<br />
Version 1.0, 2008<br />
1.1. Attendance<br />
Introduction<br />
SECTION 1<br />
General Rules<br />
Attendance in laboratory is mandatory. An unexcused absence results in the loss of all<br />
points associated with that laboratory (i.e., pre-laboratory quiz, laboratory project grade).<br />
If you have a university excused absence (such as illness, etc), you have one week to show the<br />
excuse to the course instructor (not teaching assistant) or the absence will not be excused.<br />
If you will miss a laboratory due to religious observance, you must inform the<br />
course instructor (not teaching assistant) the week BEFORE the absence, or<br />
the absence will not be excused. If you will miss two sequential weeks due to<br />
religious observance, you must inform the instructor (not teaching assistant)<br />
that you will be missing two laboratory periods BEFORE the absences, or the<br />
absences will not be excused. If the absence is excused by the course instructor, the<br />
course instructor will make arrangements with the teaching assistants for the laboratory to<br />
be made-up during a separate laboratory section.<br />
1.2. Laboratories<br />
There are 14 laboratories, including the check-in/introductory laboratory and the checkout/laboratory<br />
practical meeting. Grades will be determined from pre-laboratory quizzes,<br />
laboratory technique and safety, laboratory reports, laboratory related questions, and the<br />
laboratory practical.<br />
1.3. Tardiness<br />
It is your responsibility to attend class and to be punctual. Pre-laboratory quizzes will be<br />
given at the beginning of class. Tardiness will not result in additional time being allotted<br />
for pre-laboratory quizzes.<br />
1.4. Safety<br />
An open book safety examination, worth 5 points, will be given during the first prelaboratory<br />
period. Students must score a 3/5 on this examination. Failure to do so will<br />
result in the student being barred from the laboratory, until such time as a 3/5 is achieved.<br />
(Laboratories that are missed due to failure of the safety examination cannot be made-up.)<br />
Moreover, all students will be required to sign the Laboratory Safety Agreement given<br />
at the end of Section 3. Failure to do so will result in removal from the laboratory.<br />
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c○2008 QC Chemistry and Biochemistry
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1.5. Pre-laboratory quizzes<br />
All pre-laboratory quizzes will be 30 minutes in length and will be given at the<br />
beginning of the laboratory period. Additional time will not be given to students who<br />
are tardy. These quizzes will have three parts:<br />
(1) Post-laboratory questions and questions from the Report Sheet of the previous<br />
experiment.<br />
(2) Safety questions about the current experiment.<br />
(3) Pre-laboratory questions from the current experiment.<br />
1.6. Laboratory projects<br />
A complete laboratory project consists of the following documents, which should be stapled<br />
together in the order listed:<br />
(1) Hard copy of the laboratory report<br />
(2) The pre-laboratory questions<br />
(3) The laboratory report sheet<br />
(4) The post-laboratory questions<br />
The completed project (i.e., Items 1-4) must be given to the laboratory instructor at the<br />
beginning of the period on the date due (see the schedule in Section 2). In addition to<br />
this package, an electronic version (i.e., Word or WordPerfect) of the laboratory report<br />
(excluding pre-laboratory and post-laboratory questions and the laboratory report sheet)<br />
must also be uploaded to the Blackboard site for the course on the date due. The electronic<br />
report will check for academic dishonesty using both internet sources and previously submitted<br />
reports. Failure to submit an electronic version of the report will result<br />
in a zero on the laboratory report. Instructions for submission of a report through<br />
Turn-it-in are given in Section 5.<br />
1.7. Laboratory reports<br />
A style guide for the laboratory reports is included in Section 4. Unless specified by<br />
the laboratory instructor, laboratory reports are limited in length to 6 pages,<br />
excluding Figures and Tables.<br />
1.8. <strong>Academic</strong> dishonesty<br />
While it is natural to discuss experiments among each other (especially your laboratory<br />
partner), instances of academic dishonesty will NOT be tolerated on any assignment and<br />
will be treated in accordance with university policy. This policy can be found at:<br />
http://www1.cuny.edu/portal ur/content/2004/policies/image/policy.pdf<br />
Electronic versions of laboratory reports will be submitted to Turn-it-in software<br />
and checked for academic dishonesty. Turn-it-in checks both internet<br />
sources and previously submitted reports. We should note here that copying and<br />
downloading graphs from the internet, without express permission of the instructor, constitutes<br />
plagiarism (even if referenced).
1.9. Grading<br />
Course grading:<br />
• Safety examination and Pre-laboratory quizzes: 20% of grade<br />
• Laboratory assignments: 60% of grade<br />
• Laboratory practical: 20% of grade<br />
Any student missing a laboratory with an university excused absence will be given a makeup<br />
laboratory during the fourteenth week.<br />
Grading for a Laboratory Project:<br />
(1) Laboratory report ∗ : 34% of grade<br />
• Style guide formatting (7%)<br />
• Written report (27%)<br />
(2) Pre-laboratory questions: 20% of grade<br />
(3) Report sheet: 13% of grade<br />
(4) Post-laboratory questions: 20% of grade<br />
(5) Safety and laboratory technique: 13% of grade<br />
∗ Failure to submit an electronic version of the laboratory report through Turn-it-in via<br />
Blackboard will result in the loss of these points.<br />
Grade distribution:<br />
A+ 95.5 - 100 % C+ 70.5 - 75.4 %<br />
A 87.5 - 95.4 % C 63.5 - 70.4 %<br />
B+ 82.5 - 87.4 % D 49.5 - 63.4 %<br />
B 75.5 - 82.4 % F < 49.5 %<br />
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QC Chemistry Laboratory Manual<br />
Version 1.0, 2008<br />
Introduction<br />
SECTION 2<br />
Schedule<br />
Date Session Pre-laboratory (60 min) Laboratory (120 min) Projects due<br />
1 <strong>Syllabus</strong> and safety Experiment 1: Basic<br />
2 Safety exam. Significant<br />
laboratory techniques<br />
Experiment 2: Density. Experiment 1<br />
figures and error analysis.<br />
Project.<br />
3 Pre-laboratory quiz. Experiment 3: Law of Experiment 2<br />
Chemical Formulas. definite proportions. Project.<br />
4 Pre-laboratory quiz. Experiment 4: Stoi- Experiment 3<br />
Formulas and reactions. chiometry.<br />
Project.<br />
5 Pre-laboratory quiz. Experiment 5: Prepara- Experiment 4<br />
Chemical reactions. tion of a simple salt<br />
6 Aqueous chemistry. Experiment 6: Reactions<br />
in Solution.<br />
7 Pre-laboratory quiz. Experiment 6: Reac-<br />
Aqueous chemistry. tions in Solution.<br />
8 Pre-laboratory quiz. Experiment 6: Reac-<br />
Aqueous chemistry. tions in Solution.<br />
9 Pre-laboratory quiz.<br />
Acid/base chemistry<br />
Experiment 7:<br />
Acid/base titrations<br />
10 Pre-laboratory quiz. Experiment 8: Potentio-<br />
Acid/base chemistry. metric titrations<br />
11 Pre-laboratory quiz. Experiment 9: Heat of<br />
Heat and heat capacity. reaction.<br />
12 Pre-laboratory quiz. Experiment 10: Emis-<br />
Electron spectroscopy. sion and Beer’s Law.<br />
13 Pre-laboratory quiz. Experiment 11: Activity<br />
Metal reactivity and of metals<br />
14<br />
perfect gases<br />
LABORATORY PRACTICAL. Checkout.<br />
Make-up laboratory (examination and<br />
laboratory).<br />
5<br />
Project.<br />
Experiment 5<br />
Project.<br />
Experiment<br />
6 Project:<br />
Knowns.<br />
Experiment 6<br />
Project:<br />
knowns.Un-<br />
Experiment<br />
Project.<br />
7<br />
Experiment<br />
Project.<br />
8<br />
Experiment 9<br />
Project.<br />
Experiment 10<br />
Project.<br />
Experiment 11<br />
Project.<br />
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QC Chemistry Laboratory Manual<br />
Version 1.0, 2008<br />
3.1. Self protection<br />
Introduction<br />
SECTION 3<br />
Laboratory Safety<br />
• Wear safety goggles at all times while in the laboratory, even if you have completed<br />
your experiment. Prescription safety glasses can be worn, but students must obtain<br />
approval from the instructor. Contact lenses, if worn in the laboratory, do not take<br />
the place of safety goggles. In fact, some vapors can accumulate under the lens and<br />
cause damage to the eyes and, therefore, prescription glasses are a better choice<br />
for laboratory work.<br />
• Bare skin must be minimized while in the laboratory by wearing clothing that<br />
covers one’s feet, legs and body completely. Hence, closed shoes and full-length<br />
pants are required, since broken glass and spilled chemicals are all too common on<br />
the floors of chemistry laboratories. Sandals, flip-flops, short skirts, shorts, threequarter<br />
length pants, bare midriffs, bare backs and bare shoulders are not allowed.<br />
Long-sleeve shirts are recommended but not required. Long hair should be tied<br />
back. Hats are not allowed. Many synthetic materials are highly flammable and<br />
should not be worn in the laboratory.<br />
• No horseplay, joking or playing is permitted in the lab. Failure to obey this rule<br />
is cause for immediate expulsion from the laboratory.<br />
• No eating or drinking is permitted in the laboratory or in the prelaboratory classroom.<br />
The chewing of bubble gum is considered eating in the laboratory.<br />
• No visitors are allowed in the laboratory. Your friends should visit with you before<br />
or after, but not during the laboratory session.<br />
• Jewelry such as rings, bracelets and watches should be removed, since chemicals<br />
can cause severe irritation when trapped under a piece of jewelry.<br />
• Long hair should be secured. Long necklaces, neckties and/or scarves should be<br />
removed.<br />
• Never taste, smell or touch a chemical or solution unless specifically directed by<br />
your instructor to do so.<br />
• Wear disposable gloves that are appropriate for the chemical you are working with.<br />
Take them off and wash hands before you leave the laboratory.<br />
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c○2008 QC Chemistry and Biochemistry
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• Wash your hands after handling chemical and/or reagent bottles. ALWAYS wash<br />
your hands with soap and water before leaving the laboratory at the end of the<br />
period.<br />
• Cell phones are a distraction. Therefore, cell phones must be turned off during<br />
the laboratory period. If a cell phone rings, this phone will be confiscated<br />
by the laboratory instructor for the duration of the laboratory.<br />
3.2. Laboratory accidents<br />
• Know the location of all eye-wash, shower stations, fire extinguishers and fire<br />
blankets in the laboratory.<br />
• Report all accidents and injuries to your laboratory instructor immediately.<br />
• If an accident occurs, do not panic! Alert your instructor immediately. Then, take<br />
appropriate action regarding the accident (i.e., seek aid for an injury, flush with<br />
water, clean up chemical, etc.)<br />
• Whenever a chemical comes into contact with skin (hands, arms, etc.) flush the<br />
affected area with water for several minutes. Then wash thoroughly with soap and<br />
water. If the area of contact is the eyes or face, use the eyewash fountain to flush<br />
the chemicals. Do not rub the area with your hands before washing the area.<br />
• If the chemical spills over a large part of your body, remove all contaminated<br />
clothing immediately. Modesty is not an issue! Use the safety shower to wash<br />
area for at least 15 minutes. Follow any first aid procedures given on the Material<br />
Safety Data Sheet (MSDS).<br />
• For abrasions, cuts or minor burns, flush the area with water and consult with the<br />
laboratory instructor for further treatment.<br />
• Chemical spills on the bench or the floor should be treated using the following<br />
steps:<br />
(1) Alert your neighbors and the laboratory instructor immediately.<br />
(2) Clean up the spill as directed by the laboratory instructor.<br />
(3) If the substance is volatile, flammable, or toxic, warn everyone in the laboratory<br />
of the accident.<br />
• Know the individual hazards for all chemicals used during the laboratory experiment.<br />
Material Safety Data Sheets (MSDSs) for all chemicals are available at<br />
(1) http://msdssearch.com/<br />
(2) http://cunyqueens.chemwatchna.com , username: queensmsds , password:<br />
msds<br />
3.3. General laboratory safety<br />
• Do not place any objects (including pens or pencils) that have been placed on the<br />
laboratory bench in your mouth, since these objects may have picked up contaminants<br />
from the laboratory bench.<br />
• Do not work in the laboratory unsupervised.<br />
• Do not pipette liquids by mouth. Use a bulb to siphon liquids into a pipette.<br />
• Read the experiments and exercises before coming to class. This will familiarize<br />
you with any potential hazards that may exist or evolve during the exercise. Pay<br />
particular attention to any information concerning handling or safety of particular<br />
chemicals or solutions.<br />
• Do NOT perform unauthorized experiments or deviate from the experimental plan.<br />
Report unauthorized experiments to the instructor.
Fig. 3.1: NFPA label.<br />
• Assemble your laboratory apparatus at least 8 inches from the edge of the laboratory<br />
bench.<br />
• Maintain a clean and orderly laboratory desk and drawer. Keep drawers or cabinets<br />
closed and aisles free of obstructions. Do not place book bags, athletic equipment<br />
or other items on the floor near the laboratory bench.<br />
• Be aware of the actions of your neighbor as well as yourself. You could be the<br />
victim of a mistake made by a neighbor. Therefore, advise them of improper<br />
technique or unsafe practices. If necessary report them to the instructor.<br />
3.4. Chemical handling and disposal<br />
• Read the label on a bottle at least twice before using it! Using the wrong chemical<br />
in an experiment will result in erroneous results in your experiment and may lead<br />
to a serious accident.<br />
• Avoid removing large excesses of reagent from the bottle. Only dispense from the<br />
bottle the amount of reagent that the experiment requires.<br />
• Never return excess chemicals to the reagent bottle.<br />
• Do not touch, taste or smell chemicals.<br />
• Use the fume hoods to pour noxious or irritating chemicals, and to run chemical<br />
reactions that generate noxious or irritating products.<br />
• For additional information about the safe handling of chemicals (including information<br />
about dealing with laboratory fires), please see the section entitled Working<br />
Safely with Chemicals.<br />
• Dispose of chemicals using the guidelines given in the section entitled Overview of<br />
Hazardous Waste Disposal Procedures for Students.<br />
• Chemicals are often labeled according to NFPA (National Fire Protection Association)<br />
standard using the label shown in Fig. 3.1. This safety sticker has four<br />
fields, namely blue (health), red (fire), yellow (reactivity) and white (special). The<br />
numbers in the blocks of the stickers range from zero (0) to four (4) and indicate<br />
hazard severity, with zero being the least hazardous.<br />
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3.5. Cleanliness<br />
It is important to keep the laboratory as clean as possible, for safety reasons as well as<br />
aesthetic reasons. Each pair of students is responsible for their immediate desk area. Before<br />
leaving the laboratory, students should make sure that the area of the laboratory bench near<br />
their assigned drawer is clean and dry, that Bunsen burners and other shared equipment<br />
are put away in the appropriate space, and that the trough to the sink is free of any solid<br />
material. Laboratory instructors will check work areas before approving completion of<br />
the experiment. Pairs of students will be assigned dates for which they are responsible<br />
for cleaning the reagent shelves, balances and balance tables in the weighing room, and<br />
surfaces under the hoods. This duty will be rotated so that each pair of students will be<br />
responsible for general laboratory cleanliness at least once during the semester.<br />
General tips:<br />
• Place broken glassware in the broken glassware box.<br />
• Keep drawers and cabinets closed to avoid physical hazards.<br />
• Never place materials or chemical bottles on the floor.<br />
3.6. Other information<br />
If you have or suspect you may have any of the following conditions, please inform your<br />
laboratory instructor before attending your laboratory:<br />
• Pregnancy.<br />
• Wear contact lenses.<br />
• Wear synthetic finger nails (which are highly flammable).<br />
• Chronic breathing problems.<br />
• Immune system suppression.<br />
• Chronic Anemia.<br />
• Treatment with prescription drugs which may affect judgement.
3.7. Working Safely With Chemicals<br />
Supplied by <strong>Queens</strong> <strong>College</strong> Laboratory Safety Officer, Summer 2008.<br />
Last modified on August 26, 1998.<br />
Because few laboratory chemicals are without hazards, general precautions for handling all<br />
laboratory chemicals should be adopted.<br />
• It is prudent to minimize all chemical exposures. Precautions should be taken to<br />
avoid exposure by the principal routes of entry, that is, contact with skin and eyes,<br />
inhalation and ingestion.<br />
I. What Is A Hazardous Chemical?<br />
Any chemical that can harm a person or the environment.<br />
Personal hazards of chemicals fall into two major groups: Health Hazards and Physical<br />
Hazards.<br />
(1) Health Hazards (acute or chronic health effects):<br />
These chemicals include carcinogens, toxic or highly toxic agents, irritants,<br />
corrosives, sensitizers, and agents which damage the lungs, skin, eyes, or mucous<br />
membranes.<br />
(2) Physical Hazards:<br />
Chemicals that are either a combustible liquid, or a compressed gas, explosive,<br />
flammable, an organic peroxide, an oxidizer, pyrophoric, unstable (reactive), or<br />
water-reactive.<br />
II. How Can You Protect Yourself?<br />
(1) Protect Your Skin From Chemical Splashes:<br />
Wear long sleeved shirts and a skirt or long pants. Do not wear shorts or a<br />
miniskirt. Long hair and loose clothing or jewelry must be confined when working<br />
in the laboratory. Unrestrained long hair, loose or torn clothing, and jewelry<br />
can dip into chemicals or become ensnared in equipment and moving machinery.<br />
Clothing and hair can catch fire. Because synthetic fabrics are flammable and can<br />
adhere to the skin, they can increase the severity of a burn. Therefore, cotton<br />
is the preferred fabric. It is advisable to wear a laboratory coat. Wear shoes<br />
made of leather; do not wear open-toed shoes, sandals, clogs, or canvas sneakers.<br />
Wear disposable gloves that are appropriate for the chemical you are working<br />
with. Take them off and wash your hands before you leave the laboratory.<br />
(2) Protect Your Eyes From Chemical Splashes:<br />
Wear safety glasses or goggles. They have side shields and a closed top to<br />
protect your eyes from splashes of chemicals. Ordinary prescription glasses do not<br />
provide adequate protection against injury. Wear safety glasses over prescription<br />
glasses. Contact lenses offer no protection against eye injury and cannot be substituted<br />
for safety glasses and goggles. It is best not to wear contact lenses when<br />
carrying out operations where chemical vapors are present or a chemical splash<br />
to the eyes or chemical dust is possible, because contact lenses can increase the<br />
degree of harm and can interfere with First Aid and eye-flushing procedures. If<br />
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you must wear contact lenses for medical reasons, then safety glasses with side<br />
shields or tight-fitting safety goggles must be worn over the contact lenses.<br />
(3) Safe Behavior:<br />
• Avoid distracting or startling others.<br />
• Do not allow practical jokes and horseplay at any time<br />
• Use laboratory equipment only for its designated purpose.<br />
• Always wash your hands after completing your work.<br />
• Do not eat, drink, take medicine, chew gum, smoke, or apply makeup in the<br />
laboratory.<br />
(4) Safety Equipment:<br />
Do not pipette by mouth, use pipetting devices. Work inside a laboratory<br />
fume hood when necessary. Check for adequate air flow (a light piece of tissue<br />
hanging from the hood sash may help). Keep the sash lowered as far as possible.<br />
Keep your hands in and your head out of the hood.<br />
III. What Can You Do In Case Of Emergency?<br />
(1) Report All Accidents and Incidents To Your Supervisor.<br />
This may prevent a similar occurrence in the future.<br />
(2) Chemical Spill Emergency:<br />
(a) When a chemical has been spilled on the counter top or the floor:<br />
Use the Spill Cleanup Kit to contain and/or neutralize the spill. Collect all<br />
cleanup material in a closed container. Label it “Hazardous Chemical Waste”<br />
and place in chemical waste tray.<br />
(b) When a chemical has been splashed on a person:<br />
Use water from the Safety Shower or the Eyewash Station or cold water from<br />
the sink for fifteen minutes of continuous flow. Always get medical help as<br />
soon as possible.<br />
(3) Medical Emergency:<br />
When a person is overcome by fumes do the following:<br />
(a) Evacuate the laboratory.<br />
(b) Bring the person who is overcome to fresh air.<br />
(c) Get medical attention for the person in question.<br />
(4) Fire Emergency:<br />
Know your emergency exits!<br />
(a) Fire in the Laboratory<br />
• Fight the fire or flee the area? You safety is the MOST important<br />
consideration for this question.<br />
• Do NOT fight the fire if there is any possibility that you might be<br />
trapped by the fire or smoke.<br />
• Do NOT fight the fire if there is considerable heat, smoke or fumes.<br />
• Call the Fire Department before you or someone else starts to fight the<br />
fire. You may need backup.<br />
• Tell all others to get out. Leave the laboratory.<br />
• Close all doors.
Reference:<br />
• Do NOT use the elevator.<br />
• If you do decide to fight the fire and the fire is a small fire on a bench<br />
top, then smother the fire with a watch glass.<br />
• If you do decide to fight the fire and the fire is a larger fire, then grab<br />
an appropriate fire extinguisher and PASS, where PASS stands for:<br />
(P) Pull the pin on the fire extinguisher.<br />
(A) Aim the extinguisher at the base of the fire.<br />
(S) Squeeze the trigger.<br />
(S) Sweep the extinguisher from side to side.<br />
(b) A Person on Fire<br />
Do NOT run. Stop, Drop, and Roll.<br />
To use the safety shower, place the person on fire under the shower head, pull<br />
the handle and hold it until the water has extinguished all flames.<br />
To use the fire blanket, wrap the person on fire in the blanket and have the<br />
person stop, drop and roll.<br />
(c) Fire Alarm in the Building<br />
Make sure all bunsen burners are off. Evacuate the laboratory in an orderly<br />
fashion. Close all doors behind you. Do not use the elevator. Meet at<br />
a designated meeting place with the rest of your class. Wait until a Fire<br />
Marshal or Fire Warden says it is safe to return to the building.<br />
National Research Council (1995). Prudent Practice in the Laboratory. Washington,<br />
D.C. National Academy Press.<br />
Code of Federal Regulations, 29 CFR Part 1910, Subpart Z. U.S. Govt. Printing Office,<br />
Washington, DC 20402 (latest edition).<br />
13
14<br />
3.8. Emergency Response Procedure: <strong>Queens</strong> <strong>College</strong> – <strong>CUNY</strong><br />
Supplied by <strong>Queens</strong> <strong>College</strong> Laboratory Safety Officer, Summer 2008.<br />
Last modified on May 22, 2008.<br />
FIRE EMERGENCY<br />
In the event of a fire emergency, the following procedure should be followed:<br />
(1) Pull the nearest fire alarm. (Do not attempt to put out the fire if you do not<br />
know how to handle a fire extinguisher or if you do not think you can handle the<br />
incident.)<br />
(2) Notify others in the immediate area. Close all doors and evacuate to a safe location.<br />
(3) Dial 9-911 and provide the operator with the following information:<br />
• The existence of a fire emergency condition.<br />
• Specific location of the fire (building, floor, room, etc.).<br />
• Your name and location.<br />
(4) Contact <strong>Queens</strong> <strong>College</strong> Security Department at 997-5911 or 997-5912 and provide<br />
the desk officer with the same information as listed in Item 3.<br />
(5) When fire alarm has sounded, all occupants (faculty, staff and students) shall<br />
exit the building and move to a safe location (i.e., gather on the Quadrangle).<br />
Follow the directions of the Fire Department personnel, Security personnel and/or<br />
assigned Fire Wardens. Use stairways to exit the building. Never use the elevators<br />
unless directed to do so by Fire Department Personnel. Do not re-enter building<br />
until Fire Department personnel have declared the building safe for occupancy.<br />
MEDICAL EMERGENCY<br />
In the event of a medical emergency, the following procedure should be followed:<br />
(1) Dial 9-911 and provide the operator with the following information:<br />
• The existence of a medical emergency condition. Be as specific as possible<br />
about the incident.<br />
• Specific location of the emergency (building, floor, room, etc.).<br />
• Your name and location.<br />
(2) Contact <strong>Queens</strong> <strong>College</strong> Security Department at 997-5911 or 997-5912 and provide<br />
the desk officer with the same information as in Item 1.<br />
(3) Remain at your location in order to direct emergency personnel unless it may<br />
jeopardize your safety.<br />
HAZARDOUS MATERIALS EMERGENCY RESPONSE<br />
This plan was designed to reduce the potential for overexposure to hazardous chemicals in<br />
the event of a chemical spill. Proper spill containment and cleanup procedures are ordinarily<br />
obtained from material safety data sheets (MSDS’s). However, you should not take it upon<br />
yourself to contain or clean up a chemical spill if you:<br />
• Are not familiar with the chemical involved and with the potential hazards associated<br />
with the chemical.<br />
• Do not have the proper personal protective equipment (PPE).<br />
• Cannot reasonably be expected to handle the incident.<br />
We should note that you are responsible for familiarizing yourself with the<br />
chemicals (including potential hazards and the required PPE) used for a given
laboratory procedure. If you are unable to address the clean up of a chemical spill based<br />
upon the criteria listed above, then<br />
(1) Evacuate the area.<br />
(2) If the spill occurred within a laboratory, notify the instructor or principal investigator.<br />
(3) During normal business hours (8:00 am to 4:00 pm), also notify the Environmental<br />
Safety and Health Officer (ESHO) and/or the Laboratory Safety Officer (LSO).<br />
During normal business hours, the ESHO and LSO can be reached at:<br />
• ESHO: William Graffeo, (718) 997-2881<br />
• LSO: Parmanand Panday, (718) 997-4108 or (718) 997-4171<br />
• Assistant LSO: Rick Sherrick, (718) 997-4177<br />
(4) During off-hours, notify the Public Safety Desk Officer at (718) 997-5911 or (718)<br />
997-5912. The Public Safety Officer will make sure that the instructor (or principal<br />
investigator), the ESHO and the LSO are informed of the spill.<br />
(5) Let both your instructor (or principal investigator) and Safety Officer (or the<br />
Public Safety Desk Officer) know the following:<br />
• The existence of a spill incident.<br />
• Specific location of the incident (building, floor, room, etc.).<br />
• Type of material spilled, if known.<br />
• Any other information that you deem pertinent for the spill clean up.<br />
Once the spill is reported, the ESHO, LSO or Campus Patrol Officer will respond to the<br />
scene. The room will be evacuated and the affected area will be cordoned off. This area may<br />
include rooms adjacent to the area where the spill has occurred. If an injury has occurred as<br />
a result of the spill, the person reporting the spill and/or the Safety Officer will immediately<br />
notify the New York City Emergency Medical Service (see Medical Emergency above). If<br />
occupants are trapped within the affected area, or if the ESHO, LSO or instructor/principal<br />
investigator cannot be reached, then the Public Safety desk will contact the New York Fire<br />
Department to respond to the scene. For a large chemical spill, an incident report must be<br />
completed and submitted to the ESHO and the LSO. Thus, the Safety Officer will attempt<br />
to gather as much information as possible from the individuals present at the site at the<br />
time of the spill. Therefore, do not leave the temporary headquarters until you have talked<br />
to the Safety Officer.<br />
15
16<br />
3.9. Overview of Hazardous Waste Disposal Procedures for Students<br />
Supplied by <strong>Queens</strong> <strong>College</strong> Laboratory Safety Officer, Summer 2008.<br />
Last modified on May 22, 2008.<br />
<strong>Queens</strong> <strong>College</strong> faculty, staff, students, contractors, and other parties that handle or generate<br />
hazardous wastes are required to properly handle, store and label hazardous wastes<br />
and to comply with applicable federal, state and local regulations. As a student, your<br />
responsibilities are:<br />
(1) Follow the <strong>Queens</strong> <strong>College</strong> Hazardous Waste Program requirements of<br />
• Do not dispose of hazardous waste down sink drains.<br />
• Do not dispose of hazardous waste in the normal trash.<br />
• Do not dispose of hazardous waste by evaporation in fume hood.<br />
• Do not dispose of hazardous waste in broken glass container.<br />
• Hazardous waste must be collected in a compatible container which is in good<br />
condition.<br />
• All containers of hazardous waste MUST be labeled with the word Hazardous<br />
Waste and with other words identifying contents and hazards present.<br />
• All hazardous waste containers must be kept tightly capped except when<br />
adding or removing waste.<br />
• Do not mix incompatible chemicals together in the same waste container.<br />
• Do not store waste containers next to other bottles holding incompatible<br />
chemicals.<br />
• Separate incompatible chemicals into separate secondary containment trays.<br />
• Store hazardous waste containers at or near point of generation and under<br />
the control of generator.<br />
(2) Review Material Safety Data Sheets prior to working with chemicals.<br />
(3) Use appropriate personal protective equipment when working with chemicals.<br />
(4) Report any accident to laboratory instructor.<br />
(5) Report any emergency to Public Safety (Ext. 7-5911).
3.10. Laboratory Clean-up Schedule<br />
Session Group Students<br />
1<br />
2<br />
3<br />
4<br />
5<br />
6<br />
7<br />
8<br />
9<br />
10<br />
11<br />
12<br />
13<br />
17
18<br />
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Laboratory Safety Agreement<br />
I, the undersigned, have read and understand the safety instructions given in this laboratory<br />
manual. I agree to abide by these rules. I also understand that failure to obey the<br />
safety rules given above or to follow my instructors advise while in the laboratory can lead<br />
to my dismissal from the laboratory for one or more class periods, with a grade of zero for<br />
the missed experiment(s).<br />
As part of the safety lecture during the first laboratory period, an overview of chemical<br />
disposal and general laboratory safety was discussed. In particular, the items in Section<br />
3.9 were reviewed.<br />
All laboratory experiments in this manual have been checked for safety when performed<br />
according to directions. I, the undersigned, understand that I am responsible for reading<br />
all safety precautions required for performing each experiment. Because this is a chemistry<br />
laboratory, I understand that there is the potential for serious accidents if these safety<br />
precautions are not followed and acknowledge that the fundamental responsibility for safety<br />
lies with myself.<br />
Student Name (print): QC Student ID #:<br />
Student Signature: Date:<br />
Instructor Name (print): Instructor Signature:
This page was intentionally left blank.
QC Chemistry Laboratory Manual<br />
Version 1.0, 2008<br />
Introduction<br />
SECTION 4<br />
Freshman Chemistry Style Guide<br />
The laboratory report should consist of the following:<br />
(1) Abstract – One to four sentences that summarize the experiment<br />
(2) Introduction – The introduction should answer, using complete sentences, the<br />
questions given in the pre-laboratory questions.<br />
(3) Experimental – The experiment should detail the steps, techniques, and apparatus<br />
used to perform the experiment.<br />
(4) Results and Discussion – The result and discussion should give the results obtained<br />
from the experiments and should discuss these results. The details of the calculations<br />
are shown on the Report Sheet for the project. Thus, this section should<br />
not present the details of the calculations, but should discuss these calculations in<br />
words.<br />
(5) References – Any references including internet sites should be listed.<br />
(6) Tables – Any tables referenced in the text.<br />
(7) Figures – Any figures referenced in the text.<br />
(8) Appendix – The Pre-laboratory question sheet, Report sheet and Post-laboratory<br />
question sheet should be attached to the back of the laboratory report as appendices.<br />
4.1. Margins<br />
The margins should be standard paper margins, namely<br />
Top 1” Bottom 0.5”<br />
Left 1” Right 1”<br />
The page number should be located 0.5” from the bottom of the page and centered horizontally<br />
(cf. Figs. 4.1 - 4.7). The text should be 1” from the bottom of the page.<br />
4.2. Line spacing<br />
Double space except for references, tables, table captions, figure captions and title page.<br />
See examples for the format of these special cases (cf. Figs. 4.5 - 4.7).<br />
4.3. Font<br />
Times New Roman (or Times Roman or Roman) or Helvetica (or Courier or Arial). 12<br />
point type size. Reports written in different fonts will not be accepted.<br />
21<br />
c○2008 QC Chemistry and Biochemistry
22<br />
4.4. Layout<br />
Section headings should be preceded by a roman numeral and a period, be left justified, use<br />
all capital letters and be bold. The body of the text should use full paragraph justification.<br />
There should be two lines between each section. Widows (i.e., the last line of a paragraph<br />
that is carried over to a following page) and orphans (i.e., the first line of a paragraph<br />
appearing alone at the bottom of a page) will not be tolerated.<br />
4.5. Tables<br />
Tables should be placed at the end of the text after the references in consecutive order.<br />
Tables should be numbered sequentially and consecutively from the first table using roman<br />
numerals (i.e., I, II, etc.). The table caption should be located at the top of the table. Pay<br />
attention to significant figures when making tables. No table should be wrapped so<br />
that it exists on two pages. If a table will not fit on a single page, consult your instructor<br />
for how to format long tables. Fig. 4.6 gives an example of a page of tables for a laboratory<br />
report. Notice that the table is separated from the table caption by a double line and is<br />
ended by a double line. Also notice that the table headings are separated from the values<br />
by a single line. You should copy this format when typing tables.<br />
4.6. Figures<br />
Figures should be placed after the tables with one figure/page in consecutive order. Figures<br />
should be numbered sequentially and consecutively from the first figure using arabic<br />
numerals. If a figure is composed of multiple parts, each sub-part should be identified with<br />
a letter of the alphabet in sequential order from top to bottom. Do not use color on figures<br />
unless required. The figure caption should be placed below the figure.<br />
If data are obtained by scanning a parameter (such as temperature or energy), then the<br />
data should be graphed as a line. If, however, the data are obtained by analyzing different<br />
objects, then the data should be graphed as markers. If data are presented as markers<br />
and a line is drawn through the markers, you should indicate if the line is the result of a<br />
regression or is drawn as a help to the reader. Fig. 4.7 gives an example of a line drawn<br />
as a regression, while Fig. 4.8 shows an example of a line drawn to help the reader. Note<br />
how the figure captions indicate each type of line.<br />
Figures should not have color backgrounds. The fonts for axis markers and labels should<br />
match the font used in writing the report and should be at least 18 points in size. Figures<br />
When a figure is pasted into a word processors (such as Microsoft Word),<br />
4.7. Referencing<br />
References should be placed at the end of the document before the tables and figures. The<br />
references should be numbered sequentially and consecutively from the first time of use in<br />
the document. Citing references in the text should use on-line numerals in square brackets<br />
(i.e., [1]) which are spaced away from the preceding word or symbol and are placed inside<br />
punctuation. Examples are given below.<br />
• Journal article<br />
A. A. Author, B. B. Author and C. C. Author, “Article title,” Journal Abbr. Vol,<br />
start page (year).
• Non-scientific magazine or newspaper<br />
A. A. Author, “Title,” Name of magazine (date published) start page.<br />
• Web site<br />
A. A. Author (if any), Title of document, year. Title of site. http://url.of.site<br />
(accessed Month day, year).<br />
• Book<br />
A. A. Author, Title of book (Publisher, location, year), start page (if any).<br />
• Edited volume<br />
Title of book, E. E. Editor, eds. (Publisher, location, year).<br />
• Specific chapter of an edited volume<br />
A. A. Author, “Title of chapter” in Title of book, E. E. Editor, eds. (Publisher,<br />
location, year), start page.<br />
4.8. Title page formatting<br />
The title should be simple and concise. The title should be bold, in 14 pt text, with each<br />
word in the title capitalized except for simple words (e.g., a, on, the, an, of, etc). The<br />
title is centered on the top of the page. Nonstandard abbreviations and acronyms are not<br />
allowed in the title, since these abbreviations cannot be defined in the title. If the title is<br />
more than a single line, then the title is not double spaced. Skip two lines, then list the<br />
author of the paper. The name of the author should be typed in 12 pt text and centered<br />
on the page. Skip one line, then listed the affiliation of the author. This affiliation should<br />
be centered in 12 pt text and in italic. The affiliation is as follows:<br />
Department of Chemistry and Biochemistry, <strong>Queens</strong> <strong>College</strong> - <strong>CUNY</strong><br />
Course Number, Course Section, Semester<br />
Instructor: Instructor Name<br />
Skip two lines, then type the word “Abstract” in 12 pt type, bold, in all capitals, leftjustified.<br />
Skip a single line and type the abstract following the guidelines given above. Only<br />
the abstract should be on the title page. All fonts on the title page should be identical to<br />
the fonts in the body of the paper.<br />
An example laboratory report is shown in Figs. 4.1-4.8.<br />
23
24<br />
4.9. Example laboratory report<br />
ABSTRACT<br />
The Density of Various Materials<br />
John X. Smith<br />
Department of Chemistry and Biochemistry, <strong>Queens</strong> <strong>College</strong> – <strong>CUNY</strong><br />
CHEM 101.1, E5TBA, Fall 2008<br />
Instructor: Ms. Luxi Li<br />
The density, defined as mass per unit volume, of a set of regular shaped objects was obtained from<br />
the slope of a graph of mass (measured with an electronic balance) as a function of volume. The<br />
density of 1.16 g/mL indicates that the objects were either polyamide or acrylic. The density of<br />
silver/pink irregular cylinders was determined using Archimede’s principle to be 9.84 g/mL,<br />
indicating that the unknown sample is probably bismuth. Finally, the density of water and<br />
water/ethanol mixtures was obtained. These data were plotted as a function of ethanol concentration<br />
in order to generate a calibration curve. This calibration curve was used to determine that the<br />
ethanol concentration in the unknown sample was 38% by volume.<br />
1<br />
Fig. 4.1: Example title page for a laboratory report.
I. INTRODUCTION<br />
The identification of a substance is often performed using intensive properties, which are<br />
properties that do not depend on the quantity of the substance. Examples of these properties include<br />
color, odor, melting point, boiling point and density. The density of a substance is the mass m of<br />
the substance per unit volume V, or = m / V , (1)<br />
with standard units of kg/m 3 (although it is more commonly reported in units of g/cm 3 or g/mL).<br />
Density is independent of the quantity of the substance, since both the mass and the volume are<br />
proportional to one another at a fixed temperature. As the temperature changes, the volume of the<br />
substance changes which, in turn, changes the density. In this experiment, we determine the density<br />
of various solid and liquid materials.<br />
II. EXPERIMENTAL<br />
In the first procedure, we obtained a set composed of four regular shaped objects from the<br />
instructor and recorded the code number. We then used a metric ruler to determine the dimensions<br />
of each object with a precision of 0.01 cm. For the cubic object, we calculated the volume V from<br />
these measurements using<br />
V = l × w × h , (2)<br />
where l is the length in cm, w is the width in cm and h is the height in cm. The volume of cylindrical<br />
objects was determined from<br />
V = × r ¡ 2 × h , (3)<br />
where r is the radius of the cylinder. To obtain the error in the our volume, we remeasured the<br />
dimensions and recalculated the volume. The mass of the block was determined using an electronic<br />
2<br />
Fig. 4.2: Example introduction and experimental sections of a laboratory report.<br />
25
26<br />
balance. The balance pan was cleaned, a piece of weighing paper was added to the balance, and then<br />
the balance was tared to ensure an accurate measurement of the mass. Each block was individually<br />
placed on the center of the pan (re-zeroing the balance after each measurement) and the mass was<br />
recorded to the nearest 10 mg.<br />
Irregular shaped metal objects (or metal powders) cannot be physically measured in order to<br />
obtain the volume of the sample. However, we were able to determine the volume of the objects by<br />
observing the volume of water displaced by the object. In this procedure, we filled a graduate<br />
cylinder with approximately 5 mL of water. We then obtained a sample of an unknown pink/silver<br />
metal (after recording the code number) and weighed it. After determining the mass, we slowly<br />
added this sample to the water. We tapped the cylinder to dislodge any air bubbles from the metal<br />
sample, and then determined the new water volume. The difference in water volume is equivalent<br />
to the volume of the metal. The density was then calculated using eq. (1) and the identity of the<br />
unknown metal was determined by comparison with data given in [1].<br />
The density of the liquid samples in Part C was evaluated by weighing a 10 mL graduate<br />
cylinder and then adding a volume of the liquid to this cylinder. The mass of the liquid was<br />
determined by the difference in the weight of the graduate cylinder before and after the addition of<br />
the sample. The density was then calculated from eq. (1). The temperature was measured using a<br />
standard alcohol thermometer that was calibrated for the range of 0 – 100C during Experiment 1.<br />
III. RESULTS AND DISCUSSION<br />
The set obtained from the instructor for Part A consisted of one cubic and three cylinders of red<br />
plastic with code number 2A02. Table I presents the dimensions used in eqs. (2) and (3) to<br />
determine the volume as well as the mass of each objected obtained from the electronic balance.<br />
Fig. 4.3: Continuation of the example experimental section and beginning of the results<br />
and discussion section of a laboratory report.<br />
3
Rearranging eq. (1) to give<br />
m = V . (4)<br />
indicates that a graph of the mass as a function of volume should yield a straight line with an<br />
intercept of zero and with a slope that is equivalent to the density of the objects. Thus, Fig. 1<br />
presents the mass of the red plastic cube and cylinders versus the volume of the objects. A linear<br />
regression of these data gives a density of 1.16 ± 0.01 g/cm 3 . Using standard densities provided in<br />
[1], we determined that the unknown plastic blocks and cylinders are either acrylic or polyamide.<br />
Distinguishing between acrylic or polyamide would require additional physical or chemical tests.<br />
In Part B, we were given metallic pellets (Code 2B05) that had a slight pinkish tint. The mass<br />
of our sample was 8.451 g, while the volume of displaced water was 0.87 ± 0.01 mL. Substitution<br />
of these data into eq. (1) yields a density of 9.7 ± 0.1 g/mL, or 9.7 ± 0.1 g cm -3 (since 1 mL = 1 cm 3 ).<br />
Comparison of this result to standard densities in [1] indicates that the metallic pellets are bismuth.<br />
Since bismuth has a silver pink color [2], the color of our sample gives additional evidence for our<br />
identification of the unknown sample as bismuth.<br />
Table II gives the volume and mass of ethanol/water mixtures at various concentrations, along<br />
with the density determined using eq. (1). This density is plotted as a function of ethanol<br />
concentration in Fig. 2 to generate a calibration curve for ethanol/water density. A volume of 6.20<br />
mL of the unknown sample 2C03 had a mass of 5.756 g, while a volume of 6.80 mL had a mass of<br />
6.348 g. Thus, the unknown sample 2C03 has a density of 0.931 ± 0.003 g/mL. The calibration<br />
curve in Fig. 2 indicates that a density of 0.931 g/mL corresponds to an ethanol concentration of 38<br />
± 2% by volume, or 76 proof alcohol.<br />
In this experiment, we determined the density of various regular shaped objects by direct<br />
determination of the volume (using a ruler to measure the dimensions) and mass (using an electronic<br />
balance). From our data set, we obtained a density of 1.16 ± 0.01 g/cm 3 , indicating that the objects<br />
4<br />
Fig. 4.4: Continuation of the example results and discussion section of a laboratory report.<br />
27
28<br />
were made of either acrylic or polyamide. We also obtained the density of an unknown metal<br />
sample by indirectly measuring the volume (using water displacement) and directly measuring the<br />
mass. Our density of 9.7 ± 0.1 g/mL indicates that the unknown pinkish metal is probably bismuth.<br />
Finally, we generated a calibration curve of density as a function of ethanol concentration for<br />
ethanol/water mixtures. This calibration curve allowed us to determine that the unknown sample<br />
had 38% by volume ethanol.<br />
References<br />
1. “Experiment 2: Density” in Chemistry 113.1. Introduction to Chemical Techniques Laboratory<br />
Manual, C. M. Evans, F. H. Watson and G. L. Findley (<strong>Queens</strong> <strong>College</strong>, New York, 2008), p.<br />
36.<br />
2. Bismuth, 2008. Wikipedia. http://en.wikipedia.org/wiki/Bismuth (accessed August 13, 2008).<br />
Fig. 4.5: Continuation of the example results and discussion section and references of a<br />
laboratory report.<br />
5
Table I. The dimensions, volume V [calculated using eqs. (2) and (3)], and mass m of the four red<br />
plastic objects in package 2A02. The dimensions for the cubic object are given as length × width<br />
× height. The dimensions for the cylindrical objects are given as radius × height.<br />
Object Dimensions (cm) Volume (cm 3 ) Mass (g)<br />
1 2.01 ± 0.01 × 2.00 ± 0.01 × 2.02 ± 0.01 8.12 ± 0.12 9.419<br />
2 1.27 ± 0.02 × 3.01 ± 0.02 15.3 ± 0.6 17.748<br />
3 1.27 ± 0.01 × 6.00 ± 0.01 30.4 ± 0.5 35.26<br />
4 1.27 ± 0.02 × 9.00 ± 0.02 45.6 ± 1.5 52.90<br />
Table II. The volume V i and mass m i [where i = A, B for the measurements obtained by myself and<br />
my laboratory partner, respectively] for various ethanol (EtOH) concentrations (% by volume). The<br />
density i (i = A, B) for each measurement was determined using eq. (1). The temperature for all<br />
measurements was 23.4C.<br />
% EtOH V A (mL) m A (g) V B (mL) m B (g)¡A (g/mL)¡B (g/mL)<br />
0 5.60 5.548 7.22 7.182 0.991 0.995<br />
18 6.42 6.193 7.60 7.350 0.965 0.967<br />
36 5.70 5.343 7.80 7.318 0.937 0.938<br />
54 6.42 5.831 7.60 6.848 0.901 0.904<br />
72 6.38 5.447 8.50 7.350 0.865 0.860<br />
90 6.59 5.435 7.40 6.207 0.839 0.832<br />
6<br />
Fig. 4.6: Example tables for the laboratory report.<br />
29
30<br />
m (g)<br />
60<br />
50<br />
40<br />
30<br />
20<br />
10<br />
0<br />
0<br />
10<br />
20<br />
Fig. 1. The mass m (g) of various red plastic objects plotted as a function of the volume V (cm 3 ) of<br />
the object. The solid line represents a linear least square analysis of the experimental data with a<br />
regression equation of m = 1.16 ± 0.01 g cm -3 × V.<br />
7<br />
30<br />
V (cm 3 )<br />
40<br />
50<br />
60<br />
Fig. 4.7: Example graph for the laboratory report.
(g/mL)<br />
1.00<br />
0.95<br />
0.90<br />
0.85<br />
0.80<br />
0<br />
20<br />
40<br />
Fig. 2. The density (g/mL) plotted as a function of ethanol concentration (% by volume) for<br />
various ethanol/water mixtures. The solid markers are the data obtained for the stock solutions. The<br />
open marker indicates the density and volume position for unknown sample 2C03. The solid line<br />
is provided as a visual aid.<br />
8<br />
60<br />
% EtOH (by volume)<br />
80<br />
100<br />
Fig. 4.8: Example graph for the laboratory report.<br />
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QC Chemistry Laboratory Manual<br />
Version 1.0, 2008<br />
Introduction<br />
SECTION 5<br />
Instructions for Turn-it-in Assignments<br />
All laboratory reports must be submitted both in hard copy to the instructor and as<br />
an electronic version to Blackboard. The electronic version will be checked for instances of<br />
academic dishonesty using Turn-it-in software. To submit the electronic version,<br />
(1) Go to http://www.cuny.edu and log-in to the <strong>CUNY</strong> portal.<br />
(2) Go to the Blackboard website and to the Chemistry 113 course site for your section.<br />
(3) Select the Lab Reports folder under the Assignment link (cf. Fig. 5.1).<br />
(4) Within the Lab Reports folder (cf. Fig. 5.2), select View/Complete under the lab<br />
report that needs to be submitted.<br />
(5) Type your first and last name in the appropriate forms (cf. Fig. 5.3).<br />
(6) Type the title of the laboratory report in the appropriate form (cf. Fig. 5.3).<br />
(7) Click on the Browse button (cf. Fig. 5.3) to load the dialog that will allow<br />
you to select the file to be uploaded. Although the website lists several file<br />
formats that are acceptable, only Word or Wordperfect files are valid<br />
submissions for this course.<br />
(8) Select the file to be uploaded and then click okay. This will return you to the<br />
Blackboard site with the path for the file placed in the file form.<br />
(9) Click the Submit button (cf. Fig. 5.3) to submit the paper.<br />
(10) Once the paper is successfully uploaded (cf. Fig. 5.4), click the OK button to<br />
return to the Lab Reports folder (cf. Fig. 5.2) on the Blackboard Chemistry 113<br />
site.<br />
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c○2008 QC Chemistry and Biochemistry
34<br />
Fig. 5.1: The Assignments section of the Blackboard Chemistry 113 site.<br />
Fig. 5.2: The Lab Reports folder within the Assignments section of the Blackboard Chemistry<br />
113 site.
Fig. 5.3: The View/Complete page for a Turn-it-in assignment.<br />
Fig. 5.4: The page that appears after successful submission of an electronic laboratory<br />
report.<br />
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QC Chemistry Laboratory Manual<br />
Version 1.0, 2008<br />
6.1. Experiment 1. Basic Laboratory Technique<br />
Thermometer calibration line:<br />
37<br />
Introduction<br />
SECTION 6<br />
Useful information<br />
c○2008 QC Chemistry and Biochemistry
38<br />
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QC Chemistry Laboratory Manual<br />
Version 1.0, 2008<br />
1.1. Safety<br />
Experiments<br />
EXPERIMENT 1<br />
Check-in and Basic Laboratory Techniques<br />
During Check-in, you may encounter broken or chipped glassware. This glassware should<br />
be handled with care to prevent injury. Broken and/or chipped glassware should be placed<br />
in the broken glassware box. Bunsen burners, hot glassware, metal ring stands, and boiling<br />
water can cause painful and serious burns to skin. Hot glassware does not glow and,<br />
therefore, looks identical to glassware at room temperature. Thus, be careful when handling<br />
hot glassware.<br />
1.2. Check-in<br />
You will be assigned a laboratory bench and drawer containing your laboratory kit. You<br />
will be responsible for all items in this kit. Check-in allows you to confirm that your kit has<br />
all required glassware and to replace glassware that is broken or too dirty to clean. This is<br />
the only day when missing or broken items are replaced free of charge. Thus, you should<br />
report all items that are missing, scratched, corroded or otherwise unfit for use. You should<br />
also use this time to clean all of the glassware in the kit, since this will save time in the<br />
future. The condition and cleanliness of all items will be spot checked during the semester.<br />
At the end of the semester, check-out will be performed to ensure that all items in the<br />
laboratory kit are still in good shape and clean. Illustrations of the items that should be<br />
in the laboratory kit are given in Figs. 1.1 and 1.2. General rules about the laboratory kit<br />
are:<br />
• This kit is your responsibility. Missing items are replaced free of charge only on<br />
the day of check-in.<br />
• If you drop the course, you must report to room 214 to check-out immediately.<br />
• Students completing the course must check out with their regularly scheduled last<br />
lab class. There will be no late check-out.<br />
• At Check-out, missing or broken items are billed to the student. Other items must<br />
be clean, dry and flawless to be accepted for check-out.<br />
• After the last scheduled day of classes, students who have not checkedout<br />
will be charged a $50 fee in addition to the fee from missing, broken<br />
and dirty items.<br />
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c○2008 QC Chemistry and Biochemistry
40<br />
Fig. 1.1: Glassware located in the laboratory kit.
Fig. 1.2: Other non-glass items located in the laboratory kit.<br />
41
42<br />
These experiments are meant to provide your first experience in the laboratory. If you<br />
have prior laboratory experience, these exercises constitute a good review. Your instructor<br />
will give you the rotation order for the experiment. Submit all results on the Worksheet<br />
provided.<br />
1.3. Experiment 1A. Check-in<br />
Using the Desk Assignment Sheet, check your laboratory kit to ensure that all glassware<br />
and equipment is present and in good working order. Wash and dry all glassware during<br />
this time. If glassware is too dirty to be cleaned, return this glassware to the stockroom to<br />
be replaced.<br />
1.4. Weighing<br />
You must learn how to use laboratory balances. As always, the limit of readable precision<br />
of the scale should be recorded. When approaching the balance you will need the following:<br />
(1) The substance to be weighed;<br />
(2) A container or holder for the sample while on the balance;<br />
(3) A sample handling device such as a spatula; and<br />
(4) Your report sheet and a pencil or pen to record your measurement.<br />
Balances in this laboratory have a semi-automatic tare (an allowance for mass of the container<br />
or holder). On an electronic balance, ”tare equals zero” is set by depressing the bar,<br />
which is also the on/off switch: up for off, down for on, down again to tare. These balances<br />
have an automatic range selector that will change the readout precision automatically to<br />
0.01 g when the gross mass on the pan is over 35 g. The measurement precision for small<br />
masses is best if very light containers are used, such as the glassine weighing paper for dry<br />
solid samples. The precision for samples less than 30 g gross mass is 0.001 g.<br />
1.5. Experiment 1B. Mass<br />
(1) Obtain a bag of pennies from your instructor. Record the code on the bag in the<br />
appropriate location on the Experiment 1 Report Sheet.<br />
(2) Without taring, place a sheet of paper on the pan. Read and record its mass in<br />
the table on the Report Sheet. When possible, use the cover to protect the pan<br />
from air drafts to obtain higher precision.<br />
(3) Add the pennies to the pan one at a time, reading the mass after each addition.<br />
Enter each in the table given on the Report Sheet in the column entitled“Cumulative<br />
Mass.” Keep the pennies in order. Calculate the mass of each<br />
penny by subtracting; record the differences in the column entitled “Mass by Difference.”<br />
(4) Remove all the coins and weigh each individually, taring to zero. Record the mass<br />
of each coin in the table in the column entitled “Direct Weighing.”<br />
(5) Calculate the mean or average mass m of the pennies, with<br />
m = 1 <br />
m , (1.1)<br />
n<br />
where n is the total number of pennies.<br />
(6) Calculate the absolute deviation (d = |m−m|) from the mean of each mass (direct<br />
weighing) and then determine the average deviation d, where<br />
d = 1<br />
n<br />
d . (1.2)
Consider two hypotheses:<br />
Fig. 1.3: Bunsen burner connected to gas valve.<br />
(1) All Lincoln-head pennies are manufactured with equal mass (within 0.001 g), but<br />
their various histories result in different masses when measured.<br />
(2) New Lincoln-head pennies are lighter than older ones.<br />
Observation is complicated by the various histories of the pennies. Some typical problems<br />
in chemistry are illustrated here. Most obviously, the state of corrosion of the pennies<br />
represents an uncontrolled experimental variable which can be important. Had we used<br />
non-circulated coins, we would have expected better precision. On the other hand, pennies<br />
may not be very uniform even when new. Another question arises: How much experimental<br />
difference is sufficient and how consistently must it be observed for us to consider two data<br />
sets, or groups of data sets as distinctly different? This is an important question for which<br />
statistical methods provide answers. Which hypothesis do you choose, and why?<br />
1.6. Experiment 1C. Length<br />
While considering precision of reading a balance, select a wooden splint and measure its<br />
length on the inch scale and the centimeter scale. Place your results, along with those of<br />
your laboratory partner, in the appropriate table on the Report Sheet. Pay attention to<br />
the precision of the ruler during these measurements. What is the deviation and average<br />
deviation?<br />
Convert the lengths measured in inches to centimeters using the factor 2.54 cm/in.<br />
Similarly, convert the lengths measured in centimeters to inches. Pay attention to significant<br />
figures in your results.<br />
1.7. Bunsen Burner<br />
When selecting a burner, check to see that the gas needle valve on the bottom will close<br />
completely. Also check to see that the barrel of the burner will screw in and out so that<br />
the air supply to the flame can be controlled.<br />
With the burner gas valve off and the hose connected to the burner and the bench gas<br />
cock (see Fig. 1.3), turn the bench gas cock fully on and check for leaks around the burner<br />
with a match. With the air vents closed, open the burner gas valve and light the flame.<br />
The flame should be yellow and luminous.<br />
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44<br />
Stick a test tube into the flame briefly. You should observe<br />
a deposit of carbon black on the tube. When hydrocarbons such<br />
as methane [CH4 (natural gas)] burn in too little air (oxygen), the<br />
reaction is<br />
CH4 (gas) + O2 (gas) → C (sol) + 2 H2O (liq) .<br />
With a bit more air, the flame becomes hotter and blue, but carbon<br />
monoxide is formed:<br />
2 CH4 (gas) + 3 O2 (gas) → 2 CO (gas) + 4 H2O (liq) .<br />
Now adjust the air supply – you may also have to adjust the gas<br />
with the burner valve – until the flame resembles the schematic to<br />
the right. This is the hottest flame and is characterized by a blue<br />
inverted cone shape within the flame that is the so-called reducing<br />
flame. A little above the apex of the cone is the hottest area in the<br />
flame, reaching temperatures around 1500 ◦ C.<br />
Towards the top of the flame, conditions are oxidizing (high temperatures,<br />
excess O2). The well-adjusted flame completely converts<br />
methane and oxygen to carbon dioxide and water:<br />
CH4 (gas) + 2 O2 (gas) → CO2 (gas) + 2 H2O (liq) .<br />
To turn off the Bunsen burner, execute the lighting procedure in<br />
reverse. Shut the gas valve at the base of the burner, then close the<br />
close the bench gas cock.<br />
1.8. Experiment 1D. Understanding Flames<br />
Schematic of a<br />
bunsen burner<br />
flame when the<br />
flame is the<br />
hottest.<br />
Take a wooden splint and hold it with one end resting on the top of the burner. Notice how<br />
the splint is burned only on the edges of the flame. The flame under the cone is relatively<br />
cool (about 350 ◦ C). Place the other end of the splint higher in the flame. Notice that now<br />
the splint ignites uniformly. Give the splint to your instructor.<br />
1.9. Experiment 1E. Thermometer Calibration<br />
Fill a 100 mL beaker with 50 mL of ice. Then, cover this ice with water and stir. Insert<br />
the thermometer and observe the temperature. When the temperature remains constant,<br />
record the temperature as the melting point of ice (or freezing point of water).<br />
Fill a 250 mL beaker with 150 mL of water. Heat the water to boiling over a bunsen<br />
burner (cf. Fig. 1.4). When the water is boiling, immerse the thermometer and read the<br />
temperature. (Do not let the thermometer bulb touch the bottom of the beaker during this<br />
procedure.) Once the temperature is constant, record the temperature as the boiling point<br />
of water.<br />
If the results that you obtained from this procedure give a freezing point and boiling<br />
point of water that differs from the theoretical temperatures by the same amount, then<br />
this amount can be used to correct the temperatures recorded using this thermometer.<br />
If the difference between observed values and theoretical values is not identical for both<br />
the freezing point and boiling point, then plot the observed values versus the theoretical<br />
values. The line between these points will give a calibration line that can be used to correct<br />
temperatures.
Fig. 1.4: Hot water bath schematic.<br />
1.10. Experiment 1F. Measuring volumes<br />
Graduated cylinders are used for measuring volumes<br />
of a liquid. In your laboratory kit, you have<br />
two graduated cylinders: a 10 mL graduated cylinder<br />
and a 100 mL graduated cylinder. When a<br />
liquid is placed in a graduated cylinder, the liquid<br />
level in the cylinder will curve with the lowest (or<br />
highest) point being in the middle. This point is<br />
the meniscus and represents the point where one<br />
should determine the volume. To avoid errors in<br />
determining the volume, the line of sight must be<br />
perpendicular to the scale (cf. Fig. 1.5.<br />
Obtain a 250 mL graduated Erlenmeyer flask<br />
and fill with water to the 50 mL mark. Transfer<br />
the water, completely and without spilling, to the<br />
100 mL graduated cylinder. Record the volume to<br />
the correct precision. Similarly, obtain a 125 mL Fig. 1.5: Reading a graduated cylin-<br />
graduate Erlenmeyer flask and fill with water to the der.<br />
50 mL mark. Measure the volume and record to the correct precision.<br />
Fill a 50 mL graduated beaker with water to the 40 mL mark. Transfer the water to<br />
the 100 mL graduated cylinder. Record the volume to the correct precision. Similarly, fill<br />
a 250 mL beaker to the 50 mL mark. Record the volume to the correct precision.<br />
Obtain a sample from the laboratory instructor. Record the volume of this sample to<br />
the correct precision using the 10 mL graduated cylinder.<br />
1.11. Laboratory Project 1 requirements<br />
For this laboratory experiment, the laboratory project consists of the laboratory technique<br />
and safety score (2 pts), the Experiment 1 Report Sheet (10 pts) and the Experiment 1<br />
Post-laboratory questions (3 pts). Pre-laboratory questions and a laboratory report are<br />
not required to complete this laboratory project.<br />
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Desk Assignment Sheet: Chemistry 113.1<br />
Name: Student ID #:<br />
Desk Number: Section: Date:<br />
Combination: Lab Partner:<br />
1 Beaker, 50 mL 1 Evaporation Dish-procelain<br />
1 Beaker, 150 mL 2 Funnels, Short stem<br />
2 Beaker, 250 mL 1 Iron Ring<br />
1 Beaker, 400 mL 1 Medicine dropper<br />
1 Beaker, 600 mL 1 Metric ruler<br />
1 Boiling flask 1 Nichrome triangle<br />
2 Bottles, wide mouth 10 Test tubes (sm), 10 × 75 mm<br />
1 Bottles, Plastic wash, 250 mL 9 Test tubes (md), 15 × 180 mm<br />
2 Clamp, Bunsen 2 Test tubes (lg), 20 × 250 mm<br />
2 Clamp Fastener 1 Test tubes rack<br />
3 Crucibles (bottom) 1 Test tube rack-micro<br />
3 Crucible lids 1 Test tube brush<br />
1 Crucible tongs 1 Test tube holder, wood<br />
1 Erlenmeyer flask, 125 mL 1 Thermometer<br />
1 Erlenmeyer flask, 250 mL 2 Unknown vials<br />
1 Graduate cylinder, 10 mL 1 Watch glass, 3”<br />
1 Graduate cylinder, 100 mL 1 Watch glass, 4”<br />
1 Nickel spatula 1 Wire gauze<br />
Check In:<br />
Student Signature: Date:<br />
Checked in by: Date:<br />
Check Out:<br />
Student Signature: Date:<br />
Checked out by: Date:<br />
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Experiment 1. Report Sheet<br />
Name: Section:<br />
Partner: Date:<br />
Results<br />
Fill out all tables and answer all questions below. All values must have appropriate<br />
significant figures and units. Show these data to your instructor before leaving class.<br />
Experiment 1B. Mass<br />
Table B.I. The cumulative mass of the sample, obtained by adding each penny to the collection<br />
of pennies on the balance, and the mass of each penny (determined by directly<br />
weighing the individual pennies).<br />
Source Date of penny Cumulative Mass Direct Weighing<br />
Weighing Paper NAN NAN<br />
1st penny<br />
2st penny<br />
3st penny<br />
4th penny<br />
5th penny<br />
Describe each penny used in this study.<br />
1st penny:<br />
2nd penny:<br />
3rd penny:<br />
4th penny:<br />
5th penny:<br />
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50<br />
Experiment 1C. Length<br />
Table C.I. The length of a wood splint provided by the instructor measured in inches and<br />
in centimeters by myself (Measurement A) and my laboratory partner (Measurement B).<br />
Determine the average length for the sample.<br />
Measurement A in cm<br />
Measurement B in cm<br />
Average in cm<br />
Experiment 1D. Understanding Flames<br />
Write your name in the center of the wood splint and give to your instructor.<br />
Experiment 1E. Thermometer Calibration<br />
Table E.I. Measurement of the melting point and boiling point of water by myself (Measurement<br />
A) and my laboratory partner (Measurement B).<br />
Observed melting point (Tm) of ice<br />
Thermometer correction using Tm<br />
Observed boiling point (Tb) of water<br />
Barometric pressure (P )<br />
Actual Tb of water at P<br />
Thermometer correction using Tb<br />
Measurement A Measurement B
Experiment 1F. Measuring volumes<br />
Table F.I. The volume of water as determined using the graduations in the glassware (Row<br />
1) and the graduated cylinder (Row 2). The error in volume (i.e., |Row 1 - Row 2|) should<br />
be given in Row 3.<br />
Volume (mL)<br />
in glassware<br />
Volume (mL)<br />
using graduated<br />
cylinder<br />
Error in volume<br />
of glassware<br />
125 mL Erlenmeyer<br />
flask<br />
250 mL Erlenmeyer<br />
flask<br />
50 mL Beaker 250 mL Beaker<br />
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52<br />
Calculations<br />
Fill out all tables and answer all questions below. All values must have appropriate<br />
significant figures and units. To receive full credit all details for all calculations must<br />
be shown.<br />
Experiment 1B. Mass<br />
Table B.II. The mass of each penny determined by the difference using the cumulative mass<br />
in Table B.I and the mass of each penny determined by direct weighing. From these two<br />
measurements, calculate the average mass of each penny. Then, using the space below,<br />
determine the mean [i.e., eq. (1.1)] and the deviation from mean [i.e., eq. (1.2)].<br />
Source<br />
1st penny<br />
2st penny<br />
3st penny<br />
4th penny<br />
5th penny<br />
Mass by<br />
Difference<br />
Mass by Direct<br />
Weighing<br />
Average Mass<br />
Deviation from<br />
Mean<br />
Mean NAN
Experiment 1C. Length<br />
(1) What is the deviation from mean in inches for the values given in Table C.I? in<br />
centimeters?<br />
(2) Convert the average length in inches to centimeters using the factor 2.54 cm/in.<br />
(3) Convert the average length in centimeters to inches using the factor 2.54 cm/in.<br />
Experiment 1D. Understanding Flames<br />
(1) When the bunsen burner had a yellow, luminous flame, what was deposited on the<br />
test tube? How is this deposit related to the yellow flame color?<br />
(2) When the flame was set to a two zone flame, in which zone did the wooden splint<br />
burn first? Why?<br />
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54<br />
Experiment 1E. Thermometer calibration<br />
Plot the average for the two temperatures recorded with your thermometer in ◦ C as a<br />
function of the theoretical values on the graph below. Be sure to label all axis of the graph<br />
and to use the appropriate number of significant figures when labeling the graph. Use this<br />
graph and the space provided below to determine the calibration line for your thermometer.<br />
This calibration line will be used for all temperatures measured during this semester and,<br />
therefore, should be recorded in Section 6.
(1) Ethanol has a boiling point of 78.4 ◦ C and a melting point of -114.3 ◦ C. If your<br />
thermometer was placed into boiling ethanol, what temperature would it read? If<br />
the ethanol was freezing, what temperature would your thermometer give?<br />
(2) Fahrenheit and Celsius are related by<br />
t( ◦ <br />
9◦F F) =<br />
5◦ <br />
t(<br />
C<br />
◦ C) + 32 ◦ F ,<br />
while the relationship between Celsius and Kelvin is<br />
T (K) = (t( ◦ C) + 273.15 ◦ <br />
1K<br />
C)<br />
1◦ <br />
.<br />
C<br />
Using these relationships, convert the boiling point and freezing point of ethanol<br />
to Fahrenheit and Kelvin. Be sure to report your answers with the correct units<br />
and to the correct number of significant figures.<br />
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56<br />
Experiment 1F. Measuring volumes<br />
(1) Percent error in this measurement is given by<br />
% Error = |MA − ML|<br />
× 100 ,<br />
MA<br />
where MA is the more accurate measurement and ML is the less accurate measurement.<br />
Determine the percent error in the graduation of the Erlenmeyer flasks<br />
and the beakers.
Experiment 1. Post-laboratory questions<br />
Name: Section:<br />
Partner: Date:<br />
(1) A student used a graduated cylinder having volume markings every 1 mL to carefully<br />
measure 100 mL of water for an experiment. A fellow student said that by<br />
reporting the volume as “100” mL in her lab notebook, she was only entitled to<br />
one significant figure. She disagreed. Why did her fellow student say the reported<br />
volume had only one significant figure? Considering the circumstances, how many<br />
significant figures are in her measured volume? Justify your answers.<br />
(2) A healthy dog has a temperature ranging from 37.2 to 39.2 ◦ C. Is a dog with a<br />
temperature of 103.5 ◦ F within normal range?<br />
(3) Natural gas is mostly methane, a substance that boils at a temperature of 111 K.<br />
What is its boiling point in ◦ C and in ◦ F?<br />
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QC Chemistry Laboratory Manual<br />
Version 1.0, 2008<br />
2.1. Safety<br />
Experiments<br />
EXPERIMENT 2<br />
Density<br />
Certain metals, such as lead, can be toxic when ingested. Wash your hands after handling<br />
all samples. Laboratory ethanol has trace impurities of methanol and toluene. Therefore,<br />
laboratory ethanol should not be ingested. Ethanol and ethanol/water mixtures are also<br />
flammable and, therefore, should be kept away from open flames.<br />
2.2. Introduction<br />
Density ρ is defined as the ratio of the mass m of a sample to its volume V , or<br />
ρ = m<br />
. (2.1)<br />
V<br />
Mass and volume are extensive properties of matter – properties that depend on the<br />
quantities of substances. Such properties are not of themselves useful in characterizing substances.<br />
Intensive properties, on the other hand, are useful in characterizing substances.<br />
Intensive properties are often determined by ratioing two extensive properties measured at<br />
constant temperature T and pressure P . Density is an example of this kind of intensive<br />
property. When measured under known conditions of T and P , density can be used to<br />
characterize substances. Of course, two or more substances may have the same density,<br />
but for a given substance there is only one density (at constant T and P ). Thus, if you<br />
determine that a colorless liquid has a density of 1.00 g/mL at 4◦C and 1 atm, this does<br />
not prove the liquid is water. This fact is simply one piece of evidence that the substance<br />
may be water.<br />
2.3. Experiment 2A. Density of regular-shaped objects<br />
For objects with regular shapes, the volume can be easily determined by measuring the<br />
dimensions of the object with a ruler or calipers and then using the appropriate formula.<br />
In this experiment, you will determine the density of regular shaped objects.<br />
(1) Obtain a set of objects from your instructor. Record the code on the container in<br />
the appropriate spot of the Report Sheet.<br />
(2) Determine the dimensions of the objects using a ruler. This step should be performed<br />
by both you and your laboratory partner. Be sure to record the measurements<br />
to the correct precision. Place this in the appropriate table on the Report<br />
Sheet.<br />
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60<br />
Table 2.1: Densities ρ (in g/mL) of various materials.<br />
Material ρ (g/mL) Material ρ (g/mL)<br />
acrylic 1.17 maple 0.71 - 0.83<br />
aluminum 2.71 molybdenum 10.22<br />
antimony 6.62 polyamide (nylon) 1.15<br />
balsa wood 0.10 - 0.20 polypropylene 0.90<br />
bismuth 9.80 polytetrafluoroethylene (teflon) 2.2<br />
cadmium 8.65 polyurethane 1.23<br />
cedar 0.38 polyvinylchloride 1.38<br />
copper 8.94 sulfur 1.96<br />
iron 7.87 tin 7.29<br />
iron wood 1.28 - 1.37 titanium 4.51<br />
lead 11.34 tungsten 19.30<br />
magnesium 1.74 zinc 7.13<br />
(3) Determine the mass of each object and record this on the Report Sheet.<br />
(4) From these data, calculate the volume.<br />
(5) Graph the mass as a function of volume.<br />
(6) Determine the density of the material from the slope of this graph.<br />
(7) Then, identify the material (cf. Table 2.1 for density of some common materials).<br />
2.4. Experiment 2B. Density of irregular-shaped objects<br />
If the object has an irregular shape, the density must be determined using Archimedes’<br />
principle, which states [1]<br />
Any body completely or partially submerged in a fluid (gas or liquid)<br />
at rest is acted upon by an upward, or buoyant, force the magnitude of<br />
which is equal to the weight of the fluid displaced by the body.<br />
Thus, the volume of the displaced fluid is equal to the volume of a fully submerged object.<br />
In this experiment, you will determine the density of irregular shaped objects using<br />
Archimedes’ principle.<br />
(1) You and your laboratory partner should select two samples.<br />
(2) Note and record the identity of the sample along with a description of the sample.<br />
(3) Weigh each sample on the balance and record the weight.<br />
(4) Place approximately 30 mL of water in the 100 mL graduated cylinder. Record the<br />
exact volume. Remember to observe the rules for significant figures in recording<br />
your data.<br />
(5) Carefully drop the first of your two samples into the graduate cylinder. Record<br />
the new volume.<br />
(6) Using these data, determine the density of the sample.<br />
(7) Carefully remove the water from the graduate cylinder to recover the sample. Dry<br />
the sample and return it to the storage container. Then repeat steps 4-6 for the<br />
second sample.<br />
(8) Using Table 2.1, determine the material for each sample.
2.5. Experiment 2C. Density of liquids<br />
Determining the density of a liquid can be very important. For instance, the density of<br />
aqueous acids (such as HCl) depends on the concentration of the acid dissolved in water.<br />
Thus, measuring the density is one way to check the molarity of a concentrated acid. In<br />
this experiment, you will determine the density of water and ethanol/water mixtures. The<br />
procedure for determining the density of each sample is as follows:<br />
(1) Collect a small beaker containing ≤ 10 mL of ethanol and measure its temperature.<br />
(2) Place a clean dry 10 mL graduate cylinder on the balance and tare it to zero.<br />
Carefully transfer approximately 2 mL of the ethanol into the cylinder, taking<br />
care not to splash the sample on the sides of the cylinder. Record the mass.<br />
(3) Carefully read the volume occupied by the sample at the bottom of the meniscus<br />
holding the cylinder at eye level.<br />
(4) Calculate the density of the sample at the current temperature, noting the number<br />
of significant figures.<br />
(5) Add to the ethanol (Sample 1) approximately 1 mL of distilled water and mix using<br />
a clean spatula. Record the mass and the volume of the new sample (Sample 2).<br />
(6) Add approximately 2 mL of distilled water to Sample 2 and mix. Record the mass<br />
and the volume of the new sample (Sample 3).<br />
(7) add approximately 2 mL of distilled water to Sample 3 and mix. Record the mass<br />
and volume of the new sample (Sample 4).<br />
(8) Empty the graduated cylinder and dry.<br />
(9) Add approximately 2 mL of distilled water (Sample 5) to the 10 mL graduated<br />
cylinder. Record the mass and the volume.<br />
Once the volume and mass for all samples has been determined, obtain an unknown<br />
sample of a commercial alcohol from the instructor. Using the same technique above,<br />
determine the volume and mass of this unknown. Graph the density as a function of<br />
ethanol concentration (% by volume). Using this graph, determine the concentration of<br />
alcohol in the unknown sample.<br />
2.6. Laboratory Project 2 requirements<br />
For this laboratory experiment, the laboratory project consists of the laboratory technique<br />
and safety score (2 pts), the Laboratory report (5 pts), the Experiment 2 Pre-laboratory<br />
questions (3 pts), the Experiment 2 Report Sheet (2 pts), and the Experiment 2 Postlaboratory<br />
questions (3 pts). Remember that the laboratory report must be submitted<br />
as a hard copy to your instructor and as an electronic copy through<br />
Blackboard. The laboratory report is limited to 6 pages, double-spaced, excluding tables<br />
and figures. You should use the questions in the Report Sheet to help guide the writing in<br />
the laboratory report.<br />
References<br />
1. Buoyancy, 2008. Wikipedia. http://en.wikipedia.org/wiki/Buoyancy (accessed<br />
August 13, 2008).<br />
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This page was intentional left blank.
Appendix I. Experiment 2: Pre-laboratory Questions<br />
Name: Section: Grade<br />
Partner: Date:<br />
(1) List several examples of intrinsic properties.<br />
(2) List several examples of extrinsic properties.<br />
(3) When chemicals are weighed on a balance, how is the pan protected?<br />
(4) How is the density, mass and volume of an object related?<br />
(5) How is the volume of an irregular shaped object determined?<br />
(6) To correctly determine the volume in a graduated cylinder, where should your eyes<br />
be in relation to the rules on the cylinder and the meniscus of the sample?<br />
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Results<br />
Appendix II. Experiment 2: Report Sheet<br />
Name: Section: Grade<br />
Partner: Date:<br />
Fill out all tables and answer all questions below. All values must have appropriate significant<br />
figures and units. The details for all calculations must be shown for full credit to be<br />
obtained.<br />
Experiment 2A. Density of regular-shaped objects<br />
Sample code:<br />
Describe the samples.<br />
Table A.I. The height, area, volume and mass of each object determined by myself.<br />
Object Dimensions Mass<br />
A<br />
B<br />
C<br />
D<br />
Table A.II. The height, area, volume and mass of each object determined by my laboratory<br />
partner.<br />
Object Dimensions Mass<br />
A<br />
B<br />
C<br />
D<br />
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66<br />
Experiment 2B. Density of irregular-shaped objects<br />
Object A<br />
Your object code:<br />
Describe the object.<br />
Table B.I. The mass m of the object, the initial volume [i.e., Vi (H2O)] of water in the<br />
graduated cylinder, the final volume [i.e., Vf (H2O)] of water in the graduate cylinder, and<br />
the volume V of the object [i.e., V = Vf (H2O) - Vi (H2O)] determined by myself.<br />
Object B<br />
m:<br />
Vi (H2O):<br />
Vf (H2O):<br />
V :<br />
Object code from your laboratory partner:<br />
Describe the object.<br />
Table B.II. The mass m of the object, the initial volume [i.e., Vi (H2O)] of water in the<br />
graduated cylinder, the final volume [i.e., Vf (H2O)] of water in the graduate cylinder, and<br />
the volume V of the object [i.e., V = Vf (H2O) - Vi (H2O)] determined by my laboratory<br />
partner.<br />
m:<br />
Vi (H2O):<br />
Vf (H2O):<br />
V :
Experiment 2C. Density of liquids<br />
Table C.I. The volume VEtOH of 95% ethanol, total volume V and mass m for each of the<br />
ethanol/water mixtures determined by myself.<br />
Sample VEtOH V m<br />
1<br />
2<br />
3<br />
4<br />
5<br />
Unknown<br />
Table C.II. The volume VEtOH of 95% ethanol, total volume V and mass m for each of the<br />
ethanol/water mixtures determined by my laboratory partner.<br />
Sample VEtOH V m<br />
1<br />
2<br />
3<br />
4<br />
5<br />
Unknown<br />
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68<br />
Calculations<br />
Experiment 2A. Density of regular-shaped objects<br />
Table A.III. The volumes VA and VB, calculated from the dimensions given in Table A.I<br />
and A.II, respectively, the average volume Vavg and the average mass mavg for each object<br />
measured. The details for all of the calculations are given below the table.<br />
Object VA VB Vavg mavg<br />
A<br />
B<br />
C<br />
D
Experiment 2A (continued)<br />
Figure A.1. Plot the average mass mavg as a function of the average volume Vavg on the<br />
grid provided below. (Remember to label all axes and to use the appropriate significant<br />
figures.)<br />
(1) Perform a linear regression on the data in Table A.III and Fig. A.1. What is the<br />
final regression equation?<br />
(2) What is the density of the material, as determined from this regression equation?<br />
(3) This density is indicative of the material: .<br />
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70<br />
Experiment 2B. Density of irregular-shaped objects<br />
Object A<br />
(1) From the data in Table B.I, the density was determined to be:<br />
(2) This density is indicative of the material: .<br />
Object B<br />
(1) From the data in Table B.II, the density was determined to be:<br />
(2) This density is indicative of the material: .
Experiment 2C. Density of liquids<br />
Table C.III. The % concentration (by volume) of ethanol CA and CB and the densities ρA<br />
and ρB for myself (A) and my laboratory partner (B). The details of the the calculations<br />
are given below this table.<br />
Sample CA ρA CB ρB<br />
1<br />
2<br />
3<br />
4<br />
5<br />
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72<br />
Experiment 2C (continued)<br />
What is the density of the unknown sample for both measurements (yourself and your<br />
laboratory partner) as determined from the data in Tables C.I and C.II and the average<br />
density.<br />
Figure C.1. Graph the average densities ρx for Samples 1 - 5 as functions of the % ethanol<br />
(by volume) on the grid provided below. (Remember to label all axes and to use the appropriate<br />
significant figures.)<br />
(1) What is the concentration of the unknown sample, as determined from Fig. C.1?
Appendix III. Experiment 2: Post-laboratory Questions<br />
Name: Section: Grade<br />
Partner: Date:<br />
(1) A miner discovered some yellow nuggets. They weighted 0.0560 kg and had a<br />
volume of 2.91 mL at 20 ◦ C. Were the nuggets gold or pyrite (otherwise known as<br />
fool’s gold)? Note: The density of gold is 19.3 g/cm 3 and that of pyrite is 5.0<br />
g/cm 3 at 20 ◦ C.<br />
(2) Explain how an alcohol thermometer works.<br />
(3) The density of solid sand (without air spaces) is 2.84 g/mL. The density of gold is<br />
19.3 g/mL. If a 1.00 kg sample of sand containing some gold has a density of 3.10<br />
g/mL (without air spaces), what is the percentage of gold in the sample?<br />
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74<br />
(4) Fig. III.1 gives the density ρ of methanol/water mixtures as a function of %<br />
methanol (by volume). Using these data, what is the concentration of methanol<br />
in a methanol/water mixture with a density of ρ = 0.92 g/mL?<br />
Fig. III.1. The density ρ (g/mL) of methanol/water mixtures plotted as a function of<br />
% methanol (by volume) in the mixture. The solid line represents a nonlinear 4th order<br />
polynomial regression.
QC Chemistry Laboratory Manual<br />
Version 1.0, 2008<br />
3.1. Safety<br />
Experiments<br />
EXPERIMENT 3<br />
The Law of Definite Proportions<br />
Copper sulfate pentahydrate and barium chloride dihydrate are harmful if swallowed and<br />
can cause irritation to skin, eyes and respiratory tract. At high concentrations, these<br />
compound can affect the liver and kidneys. The anhydrous compounds are also harmful<br />
if swallowed. (We should note that 1 gr is the estimated lethal dose for a human.) Thus,<br />
gloves should be worn when handling the compounds of this experiment. If any of these<br />
compounds come in contact with the skin or the eyes, flush with plenty of water for at<br />
least 15 minutes. Bunsen burners, hot glassware, and metal ring stands can cause painful<br />
and serious burns to skin. Hot glassware does not glow and, therefore, looks identical to<br />
glassware at room temperature. Thus, be careful when handling hot glassware.<br />
3.2. Introduction<br />
The law of definite proportions states that when two or more elements combine to form<br />
a given compound, they do so in fixed proportions by mass. This is the same as saying<br />
the composition of a compound is fixed. For example, sodium chloride contains 39.3%<br />
by mass sodium and 60.7% by mass chlorine. In these experiments, the law of definite<br />
proportions will be used to determine the empirical formulas of hydrated ionic salts. (An<br />
empirical formula expresses the simplest whole number ratio of atoms for each element in<br />
a compound.)<br />
The previous two experiments have introduced basic laboratory techniques that will be<br />
used throughout the semester. This experiment represents the first laboratory involving basic<br />
chemical principles and reactions. However, before these principles can be investigated,<br />
an understanding of chemical formulas and nomenclature must first be developed.<br />
3.3. Chemical formulas<br />
A chemical formula represents the composition of a given substance using the basic elemental<br />
symbols. If more than one atom of an element is present in a compound, a subscript<br />
is used after the symbol to indicate the number of atoms. Thus, the chemical compound<br />
represented by the formula Fe2O3 has two atoms of iron (Fe) and 3 atoms of elemental<br />
oxygen (O). However, the mass of a single atom is difficult to measure. (For instance, the<br />
mass of a single hydrogen cation (or proton) is 1.67 × 10 −24 g.) Therefore, the mole is<br />
defined as the number of 12 C atoms in exactly 12 grams of 12 C. Moreover, the basic unit of<br />
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76<br />
Fig. 3.1: Flow chart on chemical nomenclature, adapted from [1].<br />
mass for elemental chemistry, namely the atomic mass unit (amu or dalton) is defined as 1<br />
amu ≡ 1<br />
12 the mass of an atom of 12 C = 1.6605 × 10 −24 g. Thus,<br />
1 mole = 12 g C atoms ×<br />
1 C atom<br />
19.926 × 10 −24 g C atom = 6.022 × 1023 C atoms .<br />
The constant 6.022 × 10 23 atoms (or molecules)/mole is known as Avogadro’s number.<br />
Since the mole and the atomic mass unit are defined using the same scale, 1 amu = 1<br />
g/mole. Thus, the masses given on the periodic table can also be expressed as the number<br />
of grams of the element per mole of element. The molar mass M of a compound (sometimes<br />
known as molecular weight) is obtained by summing the mass of all of the elements in a<br />
compound and, therefore, has units of g/mol. Moreover, the definition of a mole when<br />
combined with the law of definite proportions implies that a sample of H2O will have 2<br />
moles of atomic hydrogen for every 1 mole of atomic oxygen.<br />
3.4. Chemical nomenclature<br />
Simple chemical compounds are named based on the classification as covalent compounds,<br />
ionic compounds, or acids (which are a special class of covalent compounds). Covalent<br />
compounds are formed between non-metals, while ionic compounds are composed of a<br />
metal and one or more non-meals. Acids are the class of covalent compounds that result<br />
from the interaction of the hydrogen cation H + with any anion. A flow chart indicating<br />
the basic rules of nomenclature is given in Fig. 3.1 with a summary of the rules presented<br />
below.<br />
3.4.1. Covalent compounds<br />
The numbers in the chemical formula are converted into words using the Greek prefixes of<br />
1 → mono 6 → hexa<br />
2 → di 7 → hepta<br />
3 → tri 8 → octa<br />
4 → tetra 9 → nona<br />
5 → penta 10 → deca<br />
The elements are named in the same order as in the chemical formula, where elements<br />
are listed in the order of greatest electronegativity. The suffix of the last element becomes
-ide. Thus, N2O5 is dinitrogen pentaoxide, while ClO2 is monochlorine dioxide or chlorine<br />
dioxide. However, Na2O contains a metal and, therefore, is not disodium oxide. The acids,<br />
which are a class of covalent compounds will be discussed later. Organic compounds (i.e.,<br />
compounds containing only C, H, O, N, and P) have a different nomenclature which will be<br />
covered in more detail in Organic Chemistry. Some simple compounds are more generally<br />
referred to by common names, instead of the International Union of Pure and Applied<br />
Chemistry (IUPAC) name. Table 3.1 gives the names of some simple compounds that you<br />
should know as a student in chemistry. Common names are in italic.<br />
3.4.2. Ionic compounds<br />
Ionic compounds are composed of charged elements or compounds. Positively charged ions<br />
are cations, while negatively charged ions are anions. A neutral ionic compound must have<br />
charge balance (i.e., the net charge on the cations must equal the neat charge of the anions).<br />
Thus, the ionic compound formed by the reaction of Fe 3+ and Cl − must have 3 atoms of<br />
the chloride anion (Cl − ) for every iron(III) cation (Fe 3+ ) in order for the compound to be<br />
neutral. This fact implies a chemical formula of FeCl3. Ionic compounds are named by<br />
naming the cation first and then the anion.<br />
3.4.3. Cations<br />
(1) Cations from periodic table groups I, II and III have charges of +1, +2 and +3,<br />
respectively. Since the charge cannot vary for stable compounds with these cations,<br />
the unmodified metal name is used for the ion.<br />
(2) Silver, zinc and cadmium only form +1 cations and, therefore, are named using<br />
the unmodified metal name.<br />
(3) Mercury(I) ion is not stable and, therefore, always forms the cation Hg 2+<br />
2 in ionic<br />
compounds.<br />
(4) All other metal cations are named by adding a roman numeral in parentheses after<br />
the metal name to indicate the charge on the ion (known as the Stock system of<br />
nomenclature). For example, Fe 3+ is iron(III), while Pb 2+ is lead(II). Some of these<br />
metal compounds have an older nomenclature, which you will see on some of the<br />
reagent bottles in the laboratory. Table 3.2 gives the older system in comparison<br />
to the Stock system for metals that are important in freshman chemistry.<br />
, known as the ammonium ion, behaves as a Group I metal ion although it<br />
does not contain a metallic element. Thus, the ammonium ion can act as a cation<br />
in an ionic compound.<br />
(5) NH + 4<br />
Table 3.1: Names of simple compounds important in freshman chemistry.<br />
Formula Common name<br />
H2O dihydrogen oxide (water)<br />
NH3<br />
azane (ammonia)<br />
CH4<br />
methane<br />
CH3CH3<br />
ethane<br />
CH3OH methanol (wood alcohol)<br />
CH3CH2OH ethanol (alcohol)<br />
PH3<br />
phosphane (phosphine)<br />
AsH3<br />
arsine or arsinic trihydride<br />
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Table 3.2: Metal cation nomenclature: The Stock system in comparison to the older<br />
system.<br />
3.4.4. Anions<br />
Cation Stock system Older name<br />
Cu + copper(I) ion cuprous ion<br />
Cu 2+ copper(II) ion cupric ion<br />
Fe 2+ iron(II) ion ferrous ion<br />
Fe 3+ iron(III) ion ferric ion<br />
Hg 2+<br />
2 mercury(I) ion mercurous ion<br />
Hg 2+ mercury(II) ion mercuric ion<br />
Sn 2+ tin(II) ion stannous ion<br />
Sn 4+ tin(IV) ion stannic ion<br />
(1) Monoatomic anions formed from non-metal elements with sufficient extra electrons<br />
to have a rare gas configuration have names that end in -ide. Thus O2− , which has<br />
an electron configuration similar to the rare gas Ne, is named oxide. Similarly, P3− (having an electron configuration similar to the rare gas Ar) is named phosphide.<br />
(2) Table 3.3 lists the common polyatomic ions that are important in freshman chemistry.<br />
It is important to known the names and formulas of these anions<br />
and, therefore, this table should be memorized.<br />
(3) Polyatomic anions with names ending in -ite are related to the -ate anions in<br />
Table 3.3 but have one less oxygen atom. The standard -ite anions are also given<br />
in Table 3.3.<br />
(4) Anions with names having the form Per-ate are related to the -ate anions in Table<br />
3.3, but contain one additional oxygen atom. Thus, ClO − 4<br />
is the perchlorate<br />
anion.<br />
(5) Anions with names of the form Hypo-ite are related to the -ite anions in Table<br />
3.3, but have one less oxygen atom. Thus, ClO − is the hypochlorite anion.<br />
(6) Anions that are formed from the combination of an anion with a charge > −1<br />
and an H + unit are named hydrogen - ion. Thus, HS− is hydrogen sulfide ion,<br />
is dihydrogen phosphate ion.<br />
HPO 2−<br />
4 is hydrogen phosphate ion, and H2PO − 4<br />
3.4.5. Hydrates<br />
Hydrates are substances formed when water combines chemically in definite proportions<br />
with an ionic salt, thereby giving a constant ratio of water molecules to the ions of the salt.<br />
Hydrates are not mixtures, since the water is coordinatively bound to either the cation<br />
or anion or both in the salt. In CuSO4 • 5 H2O, for example, the bonding involves four<br />
water molecules coordinatively bound to the Cu 2+ ion in a square planar structure and one<br />
molecule of water bound to the sulfate ion by hydrogen bonds [cf. Fig. 3.2]. The anhydrous<br />
(without water) form of a hydrated salt is produced when all the water of hydration is lost.<br />
Some examples of hydrates are listed below:<br />
Formula Chemical name Common name<br />
(CaSO4)2 • H2O calcium sulfate hemihydrate plaster of paris<br />
CaSO4 • 2 H2O calcium sulfate dihydrate gypsum<br />
CuSO4 • 5 H2O copper (II) sulfate pentahydrate blue vitriol<br />
MgSO4 • 7 H2O magnesium sulfate heptahydrate epsom salt<br />
Na2CO3 • 10 H2O sodium carbonate decahydrate washing soda
Table 3.3: The important polyatomic anions.<br />
Formula Name Formula Name<br />
OH − hydroxide CN − cyanide<br />
O 2−<br />
2 peroxide NH − 2 amide<br />
NO − 2 nitrite NO − 3 nitrate<br />
SO 2−<br />
3 sulfite SO 2−<br />
4<br />
PO 3−<br />
3 phosphite PO 3−<br />
4<br />
sulfate<br />
phosphate<br />
ClO − 2 chlorite ClO − 3 chlorate<br />
CO 2−<br />
3 carbonate C2H3O − 2 acetate<br />
CrO 2−<br />
4 chromate Cr2O 2−<br />
7<br />
dichromate<br />
MnO − 4 permanganate SCN − thiocyanate<br />
Notice that hydrates are named by first naming the ionic salt and then adding x-hydrate,<br />
where x− is the appropriate Greek prefix (cf. Section 3.4.1) to indicate the number of<br />
water molecules associated with salt. The • in the formula indicates a kind of chemical<br />
bond that usually can be easily broken. For example, magnesium sulfate heptahydrate can<br />
be converted to anhydrous magnesium sulfate by heating:<br />
3.4.6. Acids<br />
MgSO 4 • 7H2O (s) → MgSO 4 (s) + 7H2O (g) . (3.1)<br />
Acids are covalent compounds formed from the hydrogen cation and any of the anions.<br />
Although these compounds are covalent, the hydrogen cation can be easily removed when<br />
the acid is in solution. Thus, acids also have some properties of ionic compounds. Because<br />
of this uniqueness, acids have a different nomenclature standard with the rules:<br />
(1) Acids formed with -ide anions are named hydro-ic acid. Thus, HCl (which<br />
contains a chloride anion) is hydrochloric acid.<br />
(2) Acids formed with -ate anions (including per-ates) are named -ic acid. As an<br />
example, H2SO4 is sulfuric acid and HClO4 is perchloric acid.<br />
(3) Acids formed with -ite anions (including hypo-ites) are named -ous acid. Thus,<br />
HNO2 is nitrous acid, while HClO is hypochlorous acid.<br />
Fig. 3.2: Schematic picture of the CuSO4 • 5 H2O compound with the Cu 2+ ion forming<br />
a square planar structure involving four water molecules, while the fifth water molecule is<br />
hydrogen bonded to the sulfate counter ion [i.e., SO 2−<br />
4 ].<br />
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80<br />
See Section 3.3.4, Item (6) for the nomenclature of acidic anions (i.e., anions formed<br />
from the loss of a single H + from an acid that has more than one hydrogen cation available).<br />
3.5. Experiment 3A. Qualitative properties of hydrates<br />
Efflorescence is the process by which a hydrated salt loses water at room temperature and<br />
atmospheric pressures. On the other hand, the property of some salts to collect moisture<br />
from the air and dissolve in it is called deliquescence. A compound is hygroscopic if<br />
absorption of water from the atmosphere occurs without dissolution of the compound. At<br />
the beginning of the laboratory, your instructor placed watch glasses of calcium chloride,<br />
sodium carbonate, and lithium chloride on a watch glass in order to expose these compounds<br />
to air. In the appropriate table on the Report Sheet describe each of these compounds<br />
at the beginning of the laboratory and towards the end of the laboratory.<br />
3.6. Experiment 3B. Composition of a hydrate<br />
In this experiment, the laboratory instructor will give you and your laboratory partner<br />
two hydrated salts chosen from copper sulfate, barium chloride, and sodium sulfate. The<br />
difference in the mass of the anhydride and the hydrate will then be used to determine the<br />
mass of water in the hydrate and, therefore, the empirical formula of the hydrate. The<br />
procedure for this study is as follows:<br />
(1) Weigh a clean, dry, labeled crucible. Record the weight on the Report Sheet.<br />
(2) Introduce about 1 - 2 grams of the pulverized hydrated salt. Note the appearance<br />
and color of the solid.<br />
(3) Weigh the crucible and contents. Record this weight on the Report Sheet.<br />
(4) Setup a wire triangle on the iron ring over a bunsen burner. (Ensuring that the<br />
wire triangle will hold the crucible in an upright position.)<br />
(5) Heat the crucible and contents in the hottest part of the flame for 5 - 10 minutes.<br />
(The bottom of the crucible should turn a dull red during heating.) Initially, the<br />
hydrate should be heated slowly by waving the burner flame fairly rapidly under<br />
the crucible. If the material begins to boil or crackle, the heating is too intense<br />
and splattering may occur. Within approximately 1 minute, the material should<br />
become drier and stronger heat can be applied. At the end of the 5 - 10 minute<br />
period of heating, again heat slowly to allow the crucible to cool slightly before<br />
transfer.<br />
(6) Using clean crucible tongs, transfer the crucible to a desiccator and allow the<br />
crucible to cool to room temperature.<br />
(7) When cool, weigh the dish and the anhydride and record this weight on the Report<br />
Sheet.<br />
(8) Heat the crucible in the flame again for 5 minutes, place in desiccator and allow the<br />
crucible to cool. Once cool, weigh the sample again. Continue the heat/cool/weigh<br />
cycle until the mass of the sample remains constant. Be sure to record all of your<br />
measurements on the Report Sheet.<br />
(9) Place a thermometer in the anhydrous salt and record the temperature.<br />
(10) Add water a few drops at a time to convert the anhydride back to the hydrate.<br />
Record the temperature (once the temperature is constant).
3.7. Laboratory Project 3 requirements<br />
For this laboratory experiment, the laboratory project consists of the laboratory technique<br />
and safety score (2 pts), the Laboratory report (5 pts), the Experiment 3 Pre-laboratory<br />
questions (3 pts), the Experiment 3 Report Sheet (2 pts), and the Experiment 3 Postlaboratory<br />
questions (3 pts). Remember that the laboratory report must be submitted<br />
as a hard copy to your instructor and as an electronic copy through<br />
Blackboard. The laboratory report is limited to 6 pages, double-spaced, excluding tables<br />
and figures. You should use the questions in the Report Sheet to help guide the writing in<br />
the laboratory report.<br />
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Appendix I. Experiment 3: Pre-laboratory Questions<br />
Name: Section: Grade<br />
Partner: Date:<br />
(1) What should you do if any of the solid compounds come in contact with your skin?<br />
(2) Heptahydrate implies how many water molecules are complexed to a salt?<br />
(3) Name the following: (a) (NH4)2S, (b) H2CO3, (c) I2, and (d) AlCl3 • 6 H2O.<br />
(4) Write the chemical formula for the following: (a) barium chloride, (b) ferrous<br />
sulfate, (c) disulfur dichloride, and (d) sodium hydrogen carbonate.<br />
(5) If 3.5 g of CuSO4 • 5 H2O (s) undergoes dehydration, what is the mass of the<br />
gaseous water produced?<br />
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Results<br />
Appendix II. Experiment 3: Report Sheet<br />
Name: Section: Grade<br />
Partner: Date:<br />
Fill out all tables and answer all questions below. All values must have appropriate<br />
significant figures and units.<br />
Experiment 3A. Qualitative properties of hydrates<br />
Table A.I. The information on the reactants obtained during the performance of Experiment<br />
3A.<br />
calcium chloride<br />
washing soda<br />
lithium chloride<br />
(1) Which crystals deliquesce?<br />
(2) Which crystals effloresce?<br />
Initial description Final description<br />
(3) Explain why one sample gained water and why one lost water.<br />
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86<br />
Experiment 3B. Composition of a hydrate<br />
Table B.I. The information, obtain during the performance of Experiment 3B, on the hydrates<br />
given to me.<br />
Hydrate 1 Hydrate 2<br />
Name of salt in hydrate:<br />
Formula of salt in hydrate:<br />
Mass of evaporating dish:<br />
Mass of dish and hydrate:<br />
Mass of hydrate:<br />
Mass of dish after heating*:<br />
Mass of anhydride:<br />
Temperature before water addition:<br />
Temperature after water addition:<br />
Color before heating:<br />
Color after heating:<br />
Color after adding water:<br />
*The mass after heating should only be entered after the crucible and contents have<br />
reached constants mass. Use the table below to monitor the mass of the crucible during the<br />
heat/cool/weigh cycles for your hydrates. (Please note that all of the cycles listed below<br />
may not be necessary.)<br />
Mass of dish after heating<br />
Hydrate 1 Hydrate 2<br />
Cycle 1<br />
Cycle 2<br />
Cycle 3<br />
Cycle 4<br />
Cycle 5<br />
Cycle 6
Table B.II. The information, obtain during the performance of Experiment 3B, on the<br />
hydrates given to my laboratory partner.<br />
Hydrate 1 Hydrate 2<br />
Name of salt in hydrate:<br />
Formula of salt in hydrate:<br />
Mass of evaporating dish:<br />
Mass of dish and hydrate:<br />
Mass of hydrate:<br />
Mass of dish after heating*:<br />
Mass of anhydride:<br />
Temperature before water addition:<br />
Temperature after water addition:<br />
Color before heating:<br />
Color after heating:<br />
Color after adding water:<br />
*The mass after heating should only be entered after the crucible and contents have<br />
reached constants mass.<br />
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Calculations for Experiment 3B<br />
Use the information in Tables B.I and B.II to answer the following questions for the hydrates<br />
studied by both you and your laboratory partner. All values must have appropriate<br />
significant figures and units.<br />
(1) What evidence of a chemical change did you observe when the hydrated sample<br />
was heated?<br />
(2) What evidence of a chemical change did you observe when water was added to the<br />
anhydrous sample?<br />
(3) What is the mass m H2 O of the water in the hydrate (determine by subtracting the<br />
mass m an of the anhydride from the mass m hy of the hydrate) for (a) Hydrate 1<br />
and (b) Hydrate 2?
(4) What is the percentage of water in the hydrate for (a) Hydrate 1 and (b) Hydrate<br />
2? The percentage of water can be determined by<br />
%H2O = mH2O × 100 ,<br />
mhy where mH2O is the mass of water in the hydrate and mhy is the mass of the hydrate.<br />
(5) How many moles of water were in the sample from (a) Hydrate 1 and (b) Hydrate<br />
2? The number of moles n H2 O of water in the sample can be obtained using<br />
n H2 O = m H 2 O<br />
M H2 O<br />
where M H2 O is the molar mass of water.<br />
,<br />
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90<br />
(6) How many moles of anhydride were created in (a) Hydrate 1 and (b) Hydrate 2?<br />
The number of moles n an of the anhydride in the sample can be obtained using<br />
n an = m an<br />
M an<br />
where M an is the molar mass of the anhydride.<br />
(7) How many moles of water are associated with a single mole of anhydride in (a)<br />
Hydrate 1 and (b) Hydrate 2? [Determine this by dividing the moles n H2 O of water<br />
by the moles n an of anhydride.]<br />
(8) What is the formula for the hydrate [i.e., anhydride • x H2O, where x is the ratio<br />
in question (7)] that was thermally decomposed in (a) Hydrate 1 and (b) Hydrate<br />
2?<br />
,
Appendix III. Experiment 3: Post-laboratory Questions<br />
Name: Section: Grade<br />
Partner: Date:<br />
All values must have appropriate significant figures and units.<br />
(1) Rochelle salt is the tetrahydrate of the ionic salt KNaC4H4O6. Write the formula<br />
for Rochelle salt.<br />
(2) Describe (a) the three situations in which Greek prefixes are used and (b) when<br />
Roman numerals are used in naming chemical compounds.<br />
(3) How many moles of atoms are there in 48 g of molecular oxygen?<br />
(4) If 5.051 g of magnesium sulfate heptahydrate is heated to remove all water, what<br />
is the mass of the anhydride formed?<br />
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QC Chemistry Laboratory Manual<br />
Version 1.0, 2008<br />
4.1. Safety<br />
Experiments<br />
EXPERIMENT 4<br />
Stoichiometry of a Reaction<br />
Copper sulfate pentahydrate is harmful if swallowed and can cause irritation to skin, eyes<br />
and respiratory tract. At high concentrations, this compound can affect the liver and<br />
kidneys. If any of this compound comes in contact with the skin or the eyes, flush with<br />
plenty of water for at least 15 minutes. Methanol is flammable and should be heated with<br />
care. Bunsen burners, hot glassware, and metal ring stands can cause painful and serious<br />
burns to skin. Hot glassware does not glow and, therefore, looks identical to glassware at<br />
room temperature. Thus, be careful when handling hot glassware.<br />
4.2. Introduction<br />
A very common and useful type of reaction is the displacement reaction, which occurs when<br />
a metal displaces another metal in a solution with a single ionic salt. Displacement reactions<br />
between metals occur when one metal is more active than another metal and usually involve<br />
the oxidation of one metal and the reduction of the other metal. Oxidation refers to the<br />
process in which an atom, ion, or molecule loses electrons, while reduction implies that an<br />
atom, ion, or molecule gains electrons. A useful mnemonic device to remember this is OIL<br />
RIG, or Oxidation Is Loss (of electrons) and Reduction Is Gain (of electrons). In this<br />
experiment, we will use stoichiometric principles to determine the oxidation state of iron<br />
ions (i.e., Fe 2+ or Fe 3+ ) formed during the reaction of copper sulfate (i.e, CuSO4) with<br />
solid iron (i.e., Fe 0 ).<br />
4.3. Calculations Involving Concentration<br />
Before we can begin to study solution chemistry, an understanding of concentration must<br />
first be developed. Concentration is the ratio of amount of solute to the amount of solvent<br />
or solution. A solution is a homogeneous mixture of two or more molecules or ions with one<br />
of the molecules (or ions) being the solvent and all others being the solutes. Solutes are<br />
dissolved into the solvent. In Experiment 2, you measured the density of ethanol/water solutions<br />
and plotted these data as a function of percent concentration by volume of ethanol.<br />
However, percent concentration is not the most useful measure of concentration when working<br />
with chemical reactions. Molar concentration, or molarity M, of a solution is defined<br />
as the number of moles of the solute per liter of solution, and is the most widely used measure<br />
of concentration. Other measures of concentration [e.g., molality (moles of solute/kg<br />
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of solvent), normality (equivalents of solute/liter of solution) and parts per million (ppm)]<br />
will be introduced later. Below, we have shown two examples that illustrate how molarity<br />
is calculated and how molarity is used in solution chemistry.<br />
4.3.1. Calculation of molarity<br />
If 8.5 grams of ammonia (having a molar mass of 17.031 g/mole) is dissolved in 500 mL of<br />
water, the molarity would be determined by first calculating the number of moles of NH3<br />
in solution and by then dividing the number of moles by the total volume of the solution.<br />
In other words,<br />
<br />
1 mol NH3<br />
moles NH3 = 8.5 g NH3 = 0.499 mol NH3<br />
17.031 g NH3 molarity NH 3 =<br />
0.499 mol NH3<br />
500 mL<br />
4.3.2. Molarity in solution chemistry<br />
<br />
1000 mL<br />
= 1.0 mol NH3/L = 1.0 M<br />
1 L<br />
If you wanted to make 750 mL (3 significant figures) of a 0.200 M aqueous solution of<br />
sodium chloride, one would calculate the number of grams of sodium chloride (s) by the<br />
following steps:<br />
(1) Determine the number of moles of NaCl needed to prepare the solution.<br />
(2) Determine the molar mass of NaCl.<br />
(3) Multiply the number of moles of NaCl needed by the molar mass of NaCl.<br />
These steps are illustrated below.<br />
moles NaCl = 750 mL solution<br />
= 0.1500 moles NaCl<br />
molar mass NaCl = 23.00 g/mol of Na<br />
= 58.45 g/molNaCl<br />
0.200moles NaCl<br />
1 L solution<br />
<br />
1mole Na<br />
1mole NaCl<br />
<br />
1000 mL<br />
1 L<br />
+ 35.45 g/mol of Cl<br />
grams NaCl = 0.1500 moles NaCl × 58.45 g/mol of NaCl = 8.767 g NaCl<br />
= 8.77 g NaCl<br />
4.4. Experiment 4. Reaction of copper sulfate with elemental iron<br />
<br />
1mole Cl<br />
1mole NaCl<br />
When elemental iron is oxidized (i.e., losses electrons), it can form two stable cations,<br />
namely iron(II) and iron(III). Since elemental iron is more active than a copper(II) cation,<br />
adding elemental iron to a solution containing the copper cation will result in a displacement<br />
reaction generating iron cations and elemental copper. However, two possible displacement<br />
reactions can occur, namely<br />
Fe 0 (s) + Cu 2+ (aq) → Fe 2+ (aq) + Cu 0 (s) , (4.1)<br />
or<br />
2 Fe 0 (s) + 3 Cu 2+ (aq) → 2 Fe 3+ (aq) + 3 Cu 0 (s) . (4.2)<br />
[Notice that both eq. (4.1) and (4.2) are mass and charge balanced and, therefore, represent<br />
chemical reaction equations (cf. Section 4.5).] In this experiment, we will determine which
eaction [i.e., eq. (4.1) or (4.2)] is consistent with experiment. Therefore, we will add an<br />
excess of copper sulfate solution to a known amount of elemental iron and will weight the<br />
product obtained from the chemical reaction. If eq. (4.1) is dominate, the number of moles<br />
of copper produced will equal the number of moles of iron reacted. If, however, eq. (4.2)<br />
is dominate, the number of moles of copper produced will larger than the number of moles<br />
of iron that reacted. The procedure for this study is as follows:<br />
(1) Weigh 1.0 g of iron filings.<br />
(2) Transfer the iron filings to a clean, dry, weighed 150 mL beaker.<br />
(3) Reweigh the 150 mL beaker containing the iron filings to verify the mass of iron.<br />
(4) In Question 1 of the Pre-laboratory questions, you were asked to calculate the<br />
amount of a 1.0 M copper(II) sulfate solution needed for the reaction given in eq.<br />
(4.2) to go to completion for a 1.0 g mass of iron. Show this calculation to your<br />
laboratory instructor for approval.<br />
(5) Add the volume of copper(II) sulfate obtained in (3) plus a 5% excess to a clean,<br />
dry Erlenmeyer flask.<br />
(6) Heat the copper sulfate solution to almost boiling.<br />
(7) Slowly add the hot copper sulfate solution to the beaker containing the iron filings.<br />
(If the addition is performed quickly, the solution will froth and material will be<br />
lost during the reaction.)<br />
(8) When the reaction has ceased, allow the copper product to settle. Then carefully<br />
decant the liquid from above the product.<br />
(9) Add approximately 10 mL of distilled water to the product and swirl the beaker<br />
to mix. Again, allow the product to settle and decant. This washes the product<br />
to remove trace amounts of iron cations. Repeat with a second 10 mL portion of<br />
distilled water.<br />
(10) Added 5 mL of methanol and swirl. Allow the product to settle and decant.<br />
Repeat with a second 5 mL portion of methanol.<br />
(11) Heat the beaker in a hot water bath to remove any remaining methanol. If necessary,<br />
carefully break up any clumps of copper with the spatula tip. (Check the<br />
spatula to ensure that you are not removing any copper from the beaker.)<br />
(12) When the product is thoroughly dry, dry the outside of the beaker and weigh the<br />
beaker to determine the mass of the product.<br />
(13) Transfer the product to a clean, dry, labeled vial for use in Experiment 5.<br />
(14) Repeat the entire procedure one more time and added this product to the labeled<br />
vial.<br />
4.5. Chemical reaction equations<br />
A chemical reaction equation (or chemical equation) uses chemical formulas to describe the<br />
chemical reaction that occurs. For example, eq. (4.1) states that the reactants Fe 0 and<br />
Cu 2+ will react to form the products Fe 2+ and Cu 0 . The right arrow is the symbol defined to<br />
mean reacts to yield. The physical state of each substance should be given in any complete<br />
chemical reaction equation, since the physical state can change the thermodynamics of the<br />
reaction. Mass and charge conservation are achieved by placing numbers in front of the<br />
chemical formulas. When both the mass and the charge are conserved (i.e., the mass and<br />
charge of the reactants equals the mass and charge of the products), the chemical equation<br />
is said to be balanced. You should always check to verify that a chemical equation<br />
is balanced before using this equation.<br />
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4.6. Laboratory Project 4 requirements<br />
For this laboratory experiment, the laboratory project consists of the laboratory technique<br />
and safety score (2 pts), the Laboratory report (5 pts), the Experiment 4 Pre-laboratory<br />
questions (3 pts), the Experiment 4 Report Sheet (2 pts), and the Experiment 4 Postlaboratory<br />
questions (3 pts). Remember that the laboratory report must be submitted<br />
as a hard copy to your instructor and as an electronic copy through<br />
Blackboard. The laboratory report is limited to 6 pages, double-spaced, excluding tables<br />
and figures. You should use the questions in the Report Sheet to help guide the writing in<br />
the laboratory report.
Appendix I. Experiment 4: Pre-laboratory Questions<br />
Name: Section: Grade<br />
Partner: Date:<br />
(1) What is the minimum volume needed to react all of 1.000 g of iron with a 1.0<br />
M aqueous solution of copper(II) sulfate for the reaction in eq. (4.2). Hint: The<br />
chemical reaction equation for an aqueous solution of copper(II) sulfate is<br />
CuSO4 (aq) → Cu 2+ (aq) + SO 2−<br />
4 (aq) .<br />
(2) In eq. (4.1) which compound is (a) oxidized and (b) reduced?<br />
(3) If copper foil is added to a (colorless) solution of silver nitrate, the solution turns<br />
blue, while the foil turns silvery. (a) What is happening? (b) Which is the more<br />
active metal: silver or copper?<br />
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(4) The combustion of a thin wire of magnesium metal in an atmosphere of pure<br />
oxygen produces the brilliant light of a flashbulb in a camera. The equation for<br />
the reaction is<br />
2 Mg + O2 → 2 MgO .<br />
(a) State in words how this equation is read. (b) Give the formula(s) of the<br />
reactants. (c) Give the formula(s) of the products. (d) Rewrite the equation to<br />
show that magnesium and magnesium oxide are solids and molecular oxygen is a<br />
gas.
Results<br />
Appendix II. Experiment 4: Report Sheet<br />
Name: Section: Grade<br />
Partner: Date:<br />
Fill out all tables and answer all questions below. All values must have appropriate<br />
significant figures and units.<br />
Table B.I. The data obtain during the performance of Experiment 4 by myself.<br />
Mass of empty 150 mL beaker:<br />
Mass of beaker + iron:<br />
Mass of iron filings:<br />
Volume of 1.0 M copper(II) sulfate used:<br />
Mass of beaker plus dry product:<br />
Mass of product:<br />
Trial 1 Trial 2<br />
Table B.II. The data obtain during the performance of Experiment 4 by my laboratory<br />
partner.<br />
Mass of empty 150 mL beaker:<br />
Mass of beaker + iron:<br />
Mass of iron filings:<br />
Volume of 1.0 M copper(II) sulfate used:<br />
Mass of beaker plus dry product:<br />
Mass of product:<br />
Trial 3 Trial 4<br />
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Calculations<br />
All values must have appropriate significant figures and units.<br />
(1) For each trial, calculate the number of moles of iron used. (The calculation for<br />
each trial should be clearly indicated to receive credit.)<br />
(2) For each trial, calculate the number of moles of copper formed.<br />
(3) Write the balanced chemical equation that is indicative of these experimental data?
(4) Why was an excess of copper(II) sulfate used?<br />
(5) What would happen if copper metal is added to iron sulfate solution? Why?<br />
(6) Extra credit (2 pts): What is the molarity of the iron solution created during<br />
this reaction?<br />
(7) Extra credit (2 pts): If the water was evaporated from the aqueous iron solution<br />
after the reaction, what ionic salt would be left as the residue?<br />
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Appendix III. Experiment 4: Post-laboratory Questions<br />
Name: Section: Grade<br />
Partner: Date:<br />
All values must have appropriate significant figures and units.<br />
(1) Write the balanced chemical reaction equations for the following: (a) iron reacts<br />
with molecular oxygen to yield iron(III) oxide, (b) silver nitrate and calcium chloride<br />
react to form calcium nitrate and silver chloride, and (c) ethane reacts with<br />
oxygen to form carbon dioxide and water.<br />
(2) The following reaction is used to extract silver impurities from gold:<br />
Au (l) + Ag (l) + Cl2 (g) → Au (l) + AgCl (s) .<br />
(a) Write the balanced chemical equation.<br />
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(b) How many grams of Cl2 gas would be required to remove the silver impurity in<br />
250 grams of 95% (by mass) pure gold? (Assume that silver is the only impurity.)
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QC Chemistry Laboratory Manual<br />
Version 1.0, 2008<br />
5.1. Safety<br />
Experiments<br />
EXPERIMENT 5<br />
Copper reactions<br />
Aqueous nitric acid and aqueous sulfuric acid are hazardous. They produce severe burns<br />
on the skin and the vapor is a lung irritant. These compounds should be handled in a<br />
fume hood while wearing safety glasses and gloves. Rinse your hands with water for 5<br />
minutes after handling the acid bottles. The gases produced during these reactions are<br />
toxic and must be avoided. Thus, when the experiment states that a procedure should be<br />
performed in the fume hood, DO so. Aqueous sodium hydroxide is also corrosive to the<br />
skin and is especially dangerous if splashed into eyes. Again, handle this compound with<br />
gloves. Copper sulfate pentahydrate is harmful if swallowed and can cause irritation to<br />
skin, eyes and respiratory tract. At high concentrations, this compound can affect the liver<br />
and kidneys. If any of this compound comes in contact with the skin or the eyes, flush with<br />
plenty of water for at least 15 minutes. Methanol is flammable and should be heated with<br />
care. Bunsen burners, hot glassware, and metal ring stands can cause painful and serious<br />
burns to skin. Hot glassware does not glow and, therefore, looks identical to glassware at<br />
room temperature. Thus, be careful when handling hot glassware.<br />
5.2. Introduction<br />
Chemical reactions are classified into three broad categories: (i) precipitation reactions, (ii)<br />
acid/base reactions, (iii) oxidation/reduction reactions and (iv) decomposition reactions.<br />
In precipitation reactions (or double displacement reactions) the ions of two soluble salts<br />
react to form an insoluble neutral compound and a different soluble salt. A good example of<br />
this type of reaction is the reaction of aqueous sodium chloride with aqueous silver nitrate<br />
to yield aqueous sodium nitrate and solid silver chloride, or<br />
NaCl (aq) + AgNO3 (aq) → NaNO3 (aq) + AgCl (s) .<br />
Acid/base reactions involve the reaction of an acid with a base to form a salt and (usually)<br />
water. These reactions will be covered in more detail during Experiments 7 and 8. Redox<br />
reactions, such as the reaction investigated in Experiment 4, involve the transfer of electrons<br />
from one atom to another. Decomposition reactions occur when a compound breaks down<br />
to form simpler substances, such as when calcium carbonate decomposes into calcium oxide<br />
and carbon dioxide under high temperatures. In this experiment, various chemical reactions<br />
involving copper and copper salts will be investigated.<br />
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5.3. Solubility<br />
Table 5.1: Solubility rules for ionic compounds in aqueous solutions.<br />
1. All compounds of the alkali metals (Group IA) are soluble.<br />
2. All salts containing ammonium, nitrate, chlorate, perchlorate,<br />
and acetate ions are soluble.<br />
3. All chlorides, bromides and iodides are soluble except when<br />
combined with silver, lead and mercury(I) cations.<br />
4. All sulfates are soluble except those combined with lead,<br />
calcium, strontium, mercury(I), and barium.<br />
5. All metal hydroxides and all metal oxides are insoluble except<br />
those of Group IA and those of calcium, strontium and<br />
barium. When metal oxides dissolve, these compounds react<br />
with water to form hydroxides.<br />
6. All salts that contain phosphate, carbonate, sulfite, and sulfide<br />
are insoluble except those of Group IA and ammonium.<br />
The reactions that will be investigated below will rely on the precipitation of insoluble<br />
salts from aqueous solutions. The formation of a precipitate can be predicted using the<br />
solubility rules, which are important rules that guide inorganic chemical reactions. Thus,<br />
the solubility rules in Table 5.3 should be committed to memory.<br />
5.4. Experiment 5A. Preparation of copper oxide<br />
In this study, you will react copper with nitric acid to form copper nitrate in solution, and<br />
then react this product with sodium hydroxide to obtain the solid copper hydroxide. The<br />
procedure is as follows:<br />
Reaction 1<br />
(1) Place 0.5 g of the copper created in Experiment 4 into a clean, dry, weighed 250<br />
mL Beaker.<br />
(2) Take the sample to the fume hood. Slowly add 4.0 mL of concentrated (16 M)<br />
nitric acid to the beaker inside the fume hood. Record your observations of the<br />
reaction on the Report Sheet.<br />
(3) Once the copper has dissolved, slowly add 75 mL of deionized water. Then, return<br />
to your laboratory bench.<br />
Reaction 2<br />
(1) While stirring the solution created in Reaction 1, add 30 mL of 3.0 M aqueous<br />
sodium hydroxide to create a copper precipitate.<br />
Reaction 3<br />
(1) Place the beaker on a wire gauze and ring on a ring stand and heat the solution<br />
from Reaction 2 to almost boiling. Do not boil the solution. Stir while heating<br />
to prevent bumping (i.e. large steam bubbles created due to non-uniform heating).<br />
(2) When the reaction is complete, remove the beaker from heat and continue to stir<br />
for a few minutes. Then, allow the product to settle.<br />
(3) Decant the solution. Rinse twice with 10 mL of water and twice with 5 mL of<br />
methanol.<br />
(4) Dry the product in a hot water bath, then weigh.
5.5. Experiment 5B. Preparation of copper sulfate pentahydrate<br />
Copper sulfate pentahydrate will be prepared by reacting copper oxide with sulfuric acid.<br />
The procedure is as follows:<br />
(1) Place 1.0 g of copper oxide into a clean, dry 50 mL flask. (Since the copper oxide<br />
must be dry, the copper oxide for this experiment will be supplied by the instructor.)<br />
(2) In the fume hood, add about 20 mL of 6 M sulfuric acid to the flask.<br />
(3) Return to your laboratory bench and place the flask on a wire gauze and ring for<br />
heating.<br />
(4) Heat the sample to almost boiling for a few minutes. Do not boil the solution.<br />
(5) If any copper(II) oxide remains, filter using a vacuum filtration apparatus, schematically<br />
shown in Fig. 5.1a. (See Section 5.6 for instructions.)<br />
(6) Transfer the filtrate to an evaporating dish and heat over a hot water bath until<br />
the volume has been reduced by one-half. See Fig. 5.1b.<br />
(7) Stop heating and allow the solution to slowly cool. If no crystals appear, reheat<br />
the evaporating dish to reduce the solution volume more and then allow the dish<br />
to cool again.<br />
(8) Once crystals begin to appear, set the evaporating dish into a shallow ice water<br />
bath to increase crystallization.<br />
(9) Filter the crystals using vacuum filtration.<br />
(10) Rinse the crystals with 5 mL of methanol while on the vacuum filtration apparatus.<br />
(11) Leave on the vacuum filtration apparatus until the crystals have dried. Then<br />
transfer the crystals to a sheet of weighing paper and weigh the product.<br />
5.6. Vacuum filtration<br />
Vacuum filtration (or suction filtration) uses a vacuum to reduce the pressure on one side<br />
of a piece of filter paper. When a solution is poured on top of this filter paper, the vacuum<br />
acts to pull the liquid (i.e., filtrate) through the filter paper quickly, leaving the solid (i.e.,<br />
precipitate) behind. To vacuum filter a sample,<br />
(1) Setup a vacuum filtration apparatus as shown in Fig. 5.1a.<br />
Fig. 5.1: Schematics of (a) an vacuum filtration setup and (b) a hot water bath setup.<br />
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(2) Place a piece of filter paper having the correct diameter on the flat area in the<br />
Buchner funnel and moisten the filter paper with the solvent in use.<br />
(3) Check the moist filter paper for creases.<br />
(4) Make sure that the vacuum line is attached, then turn on the vacuum.<br />
(5) Slowly pour the solution to be filtered into the Buchner funnel. Try to keep the<br />
solution in the center of the filter paper, which ensure that all of the precipitate<br />
is centered in the middle of the funnel.<br />
(6) Once the solution has been filtered, rinse the container with a small amount of the<br />
solvent to ensure that all of the precipitate was collected.<br />
(7) Use solvents to help dry the precipitate as specified in the experimental procedures.<br />
At this point, if clumps are forming a spatula can be used to separate the clumps.<br />
(8) Break the vacuum at the flask or the vacuum line.<br />
(9) Turn off the vacuum.<br />
5.7. Laboratory Project 5 requirements<br />
For this laboratory experiment, the laboratory project consists of the laboratory technique<br />
and safety score (2 pts), the Laboratory report (5 pts), the Experiment 5 Pre-laboratory<br />
questions (3 pts), the Experiment 5 Report Sheet (2 pts), and the Experiment 5 Postlaboratory<br />
questions (3 pts). Remember that the laboratory report must be submitted<br />
as a hard copy to your instructor and as an electronic copy through<br />
Blackboard. The laboratory report is limited to 6 pages, double-spaced, excluding tables<br />
and figures. You should use the questions in the Report Sheet to help guide the writing in<br />
the laboratory report.
Appendix I. Experiment 5: Pre-laboratory Questions<br />
Name: Section: Grade<br />
Partner: Date:<br />
Write the balanced reaction equation for the following reactions. (Remember that a balanced<br />
reaction equation includes the physical information about the compounds and is<br />
charge and mass balanced.)<br />
(1) reaction of solid copper with aqueous nitric acid and molecular oxygen to produce<br />
gaseous nitrogen dioxide and copper(II) nitrate.<br />
(2) Write the balanced reaction equation for the reaction of copper(II) nitrate with<br />
aqueous sodium hydroxide.<br />
(3) Write the balanced reaction equation for the decomposition of copper(II) hydroxide<br />
to copper(II) oxide.<br />
(4) Write the balanced reaction equation for the reaction of copper(II) oxide with<br />
aqueous sulfuric acid.<br />
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Results<br />
Appendix II. Experiment 5: Report Sheet<br />
Name: Section: Grade<br />
Partner: Date:<br />
Fill out all tables and answer all questions below. All values must have appropriate<br />
significant figures and units.<br />
Experiment 5A. Preparation of copper(II) oxide<br />
The mass of elemental copper used in this reaction is: .<br />
Reaction 1: Preparation of copper(II) nitrate<br />
The molarity of nitric acid was: .<br />
The volume of nitric acid added was: .<br />
The volume of distilled water added was: .<br />
What type of reaction is this?<br />
Observations (include color and texture changes):<br />
Reaction 2: Preparation of copper(II) hydroxide<br />
The molarity of sodium hydroxide was: .<br />
The volume of sodium hydroxide was: .<br />
What type of reaction is this?<br />
Observations (include color and texture changes):<br />
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Reaction 3: Preparation of copper(II) oxide<br />
This reaction took how much time?<br />
The mass of copper(II) oxide created was: .<br />
What type of reaction is this?<br />
Observations (include color and texture changes):<br />
Experiment 5B. Preparation of copper(II) sulfate pentahydrate<br />
The mass of copper(II) oxide used in this reaction is: .<br />
The molarity of sulfuric acid was .<br />
The volume of sulfuric acid was .<br />
The mass of copper sulfate pentahydrate produced was .<br />
What type of reaction is this?<br />
Observations (include color and texture changes):
Calculations<br />
All values must have appropriate significant figures and units.<br />
Experiment 5A. Preparation of copper(II) oxide<br />
(1) What is the molarity of the copper(II) nitrate solution after the addition of distilled<br />
water in Reaction 1?<br />
(2) How many moles of hydroxide ion (OH − ) are in the 30 mL of 3.0 M aqueous<br />
sodium hydroxide solution used in Reaction 2?<br />
(3) The limiting reactant is the reactant that controls the extent of reaction, because it<br />
is present in the smallest molar quantity. What is the limiting reactant in Reaction<br />
2?<br />
(4) Using the moles of the limiting reactant, determine the mass of copper(II) hydroxide<br />
created during Reaction 2.<br />
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(5) Using the mass of copper(II) hydroxide calculated above, determine the theoretical<br />
yield of copper(II) oxide in Reaction 3. (The theoretical yield is the mass of<br />
copper(II) oxide predicted if all reactions proceed at 100% efficiency.)<br />
(6) The percent yield of any reaction is<br />
experimental mass<br />
% yield =<br />
theoretical mass<br />
What is the percent yield of this reaction?<br />
× 100 . (5.1)<br />
(7) What steps in the reaction introduced error which, in turn, lowered the percent<br />
yield?
Experiment 5B. Preparation of copper sulfate pentahydrate<br />
(1) What is the percent yield for this reaction? Show all necessary calculations below.<br />
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Appendix III. Experiment 5: Post-laboratory Questions<br />
Name: Section: Grade<br />
Partner: Date:<br />
Describe whether the error introduced by each of the following problems would result in a<br />
high or low value for the preparation of copper oxide, or would not affect the results.<br />
(1) Some of the copper nitrate solution is splashed out of the beaker before the addition<br />
of sodium hydroxide.<br />
(2) Insufficient sodium hydroxide is added.<br />
(3) The solution bumps during the heating of copper(II) hydroxide to produce copper(II)<br />
oxide.<br />
(4) Some solid is lost in the decanting process.<br />
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(5) The washings with water and methanol are insufficient to remove all of the solution<br />
residues from the copper(II) oxide.<br />
(6) The copper(II) oxide crystals are still damp when weighed.