Final Chemistry Notebook

Stoichiometry
Molecular mass- is a number equal to the sum of the atomic masses of the atoms in a molecule. The molecular mass gives the mass of a molecule relative to that of the 12C atom, which is taken to have a mass of
12.
Example 1: Find molecular mass of Na2S
1.First you look at the periodic table identify were they are located then see what’s their atomic mass and see how many elements of each are there.
2. lastly you multiply the number of each element there is and then add them and you get the molecular mass.
Na 2*23= 46
S 1* 32 = 32 = 78 g Na2S
Example 2; FO3
1.First you look at the periodic table identify were they are located then see what’s their atomic mass and see how many elements of each are there.
2. lastly you multiply the number of each element there is and then add them and you get the molecular mass.
F 1*19 = 19
0 3* 16 = 48 = 67 g Fo3
Mole to mole- is the conversion in which we are converting moles of an elements into another mole of another element.
Example 1
For the balanced equation shown below, how many moles of C2H3F3 will react with 0.6568 moles of H2O?
4C2H3F3+11O2=>8CO2+6H2O+6F2
1.First, you must identify the amount it will reaction be and with what element. And how many moles each element has. If it not balanced balance it.
You are working with .6568 and C2H3F3 and H2O
C2H3F3 = 4 Moles
H2O = 6 moles
2.Next you must set a up a conversion to Convert 0.6568 moles of H2O to moles of C2H3F3. You must do this by canceling each
Other components they have like Moles and OR and element and you do this by diving them by each other to make them cancel out. You will use the fact that 4 moles of C2H3F3 equal to 6 moles of H2O .
.6558 MoL H2O 4 Mol C2H3F3 = 2.6272 Mol C2H3F3
6 MoL H2O = 6 = .43786667 Mol C2H3F2
3.,6568 had four the final product must have 4. Number only. After you set up the Conversion you must multiply everything on the top by itself and everything in the bottom by itself and lastly divide the two by
the bottom and you will get your result, but you must put it in Significant figures because
.43786667 Mol C2H3F2= .4378 Mol C2H3F2 This is the final answer because of significant figures.
Example 2
For the balanced equation shown below, how many moles of NO2 will react with 0.4817 moles of O2?
2N2O5=>4NO2+O2
1.First you must identify the reaction number and see how many moles each element has. If were not given a balanced equation we must balance it,
0.4817 and 4 moles NO2 and 1 mole O2
2.Next you must set a up a conversion to Convert 0.4817moles of O2 to moles of NO2. You must do this by canceling each other’s components they. You will use the fact that 1 mole of O2 equal to 4 moles of
NO2.
.4817 MoL O2 4 Mol NO2 = 1.9268 Mol NO2
1 MoL O2 = 1 = 1.9268 Mol of No2
3. You must multiply everything on the top and bottom by itself and lastly divide the top by the bottom.
1.9268 Mol of No2= 1.928 Mol of No2 This is the final answer because of significant figures and round
Mass to mass- is the conversion of grams of an element to moles of the same element than to another element than to grams of that last element Basically grams of and element to another Grans of another
elements.
Example 1
For the balanced equation shown below, how many Grams of C2H3F3 will react with 0.6568 grams of H2O?
4C2H3F3+11O2=>8CO2+6H2O+6F2
1.You first must identify each element’s atomic mass that the problem tells you to do. You find the atomic mass by looking at the periodic table below the letter if it need to be rounded you round and multiply
by the number of elements it each has the ones you must add all the products. And figure out what is equal to what. Identify how many moles each element has and the reaction .
1mole of C2H3F3 = 84 g of C2H3F3
C 2 * 12= 24 H 3 * 1= 3 F 3 * 19= 57 = 84 H 2* 1 O*16= 16 = 18 1mole of H2O = 18 g of H2O
Reaction .06568
6 moles of H2O = 4 moles of C2H3F3
2. Next you must set a up a conversion to Convert 0.6568 grams of H2O to grams of C2H3F3. You must do this by canceling each Other
components they have you first cancel grams then moles than you end with grams as the result. And use the highlighted key above to do it.
.6568 g H2O 1 Mol H2O 4 Mol C2H3F3 84 g C2H3F3 = 220.6848 g C2H3F3
18 g H2O 6 Mol H2O 1 Mol C2H3F3 = 108 = 2.04337778 g C2H3F3
3. After you set up the Conversion you must multiply everything on the top by itself and everything in the bottom by itself and lastly divide the two by the bottom and you will get your result, but you must put it
in Significant figures .
2.04337778 g C2H3F3= 2.0433 g C2H3F3 This is the final answer because of significant figures
Example 2
For the balanced equation shown below, how many grams of H2 will react with 43.5 grams of N2?
3H2+N2=>2NH3
1. You first must identify each element’s atomic mass that the problem tells you to do. You find the atomic mass by looking at the periodic table and multiply by the number of elements it each has the ones you
must add all the products. Identify what equal to each other.
H2*1= 2 = 2 N2*14= 28 1mole of H2= 2 grams of H2
1 mole of N2= 28 g of N2
3 moles of H2= 1 mole of N2
2. Next you must set a up a conversion to Convert 43.5 grams of N2 to grams of H2 . You must do this by canceling each Other
components they have you first cancel grams then moles than you end with grams as the result. And use the highlighted key above to do it.
43 .5 grams N2 1 Mol N2 3 Mol H2 2 g H2 = 261 g H2
28 g N2 1 Mol H2O 1 Mol H2 = 28 = 9.321428571 g H2
3.After you set up the Conversion you must multiply everything on the top by itself and everything in the bottom by itself and lastly divide the two by the bottom and you will get your result, but you must put it in
Significant figures.
9.321428571 g H2 = 9.32 g H2 answer because of significant figures
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