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General Chemistry Principles, Patterns, and Applications, 2011

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The empirical formula of a substance can be calculated from its percent composition,<br />

<strong>and</strong> the molecular formula can be determined from the empirical formula <strong>and</strong> the<br />

compound’s molar mass.<br />

C O N C E PTUAL P R OBLEMS<br />

1. What is the relationship between an empirical formula <strong>and</strong> a molecular formula?<br />

2. Construct a flowchart showing how you would determine the empirical formula of a compound from its<br />

percent composition.<br />

N U M E R I C A L PR O BL E M S<br />

Please be sure you are familiar with the topics discussed in Essential Skills 2 (Section 3.7 "Essential Skills 2")<br />

before proceeding to the Numerical Problems.<br />

1. What is the mass percentage of water in each hydrate?<br />

a. H 3 AsO 4·0·5H 2 O<br />

b. NH 4 NiCl 3·6H 2 O<br />

c. Al(NO 3 ) 3·9H 2 O<br />

2. What is the mass percentage of water in each hydrate?<br />

a. CaSO 4·2H 2 O<br />

b. Fe(NO 3 ) 3·9H 2 O<br />

c. (NH 4 ) 3 ZrOH(CO 3 ) 3·2H 2 O<br />

3. Which of the following has the greatest mass percentage of oxygen—KMnO 4 , K 2 Cr 2 O 7 , or Fe 2 O 3 ?<br />

4. Which of the following has the greatest mass percentage of oxygen—ThOCl 2 , MgCO 3 , or NO 2 Cl?<br />

5. Calculate the percent composition of the element shown in bold in each compound.<br />

a. SbBr 3<br />

b. As 2 I 4<br />

c. AlPO 4<br />

d. C 6 H 10 O<br />

6. Calculate the percent composition of the element shown in bold in each compound.<br />

a. HBrO 3<br />

b. CsReO 4<br />

c. C 3 H 8 O<br />

Saylor URL: http://www.saylor.org/books<br />

Saylor.org<br />

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