UNIT VII REVIEW
I. Good things to know:
 standard temperature and pressure (STP)
 mole, Avagadro’s Number, stoichiometry
 monatomic elements, diatomic elements (“magic 7”), formula units, molecules
II. Find the formula mass of the following:
__________ 1. Na2S
__________ 2. Ba(NO3)2
__________ 3. (NH4)3P
__________ 4.
__________ 5. silicon tetrafluoride
__________ 6. copper(I) sulfate
__________ 7. sodium bicarbonate
__________ 8. sulfurous acid
CuSO4  5H 2O
III. Stoichiometry
1. What is the mass of 7.50 moles of sulfur dioxide?
2. How many grams does 5.093 x 1021 atoms of iron weigh?
3. If you have a 10.2 dm3 container of helium gas at STP, how many moles are in there?
4. What is the mass of 3.02 x 1019 molecules of sulfur hexachloride?
5. What volume would 8.20 x 1025 molecules of carbon dioxide gas occupy at STP?
IV. Find the percent composition for the following:
1. Li2O
2. N2O4
4. A 0.63g sample of magnesium is heated to form 1.04g of magnesium oxide.
3. iron(III) cyanide
UNIT VII REVIEW
V. Finding Formulas
1. A compound is found to contain 1.75 grams of carbon and 46.75 grams of bromine. If the formula mass of the
compound is 331.6 g/mol.
a. What is the empirical formula?
b. What is the molecular formula?
2. A compound is found to contain 84.1% carbon and 15.9% hydrogen. If the formula mass for the compound is
found to be 114.18 g/mol.
a. What is the empirical formula?
b. What is the molecular formula?
VI. Equation Math
1) Answer the following questions using the following equation:
3 H2(g) + N2(g)  2 NH3(g)
a. How many moles of ammonia will be produced when you react 0.476 moles of hydrogen with excess
nitrogen?
b. At STP, what volume of hydrogen gas do you need to react with 3.81 L of nitrogen gas?
c. If you want to produce 10.0 g of ammonia for your cleaning product, how many grams of hydrogen
do you need?
d. If you begin with 6.50 liters of nitrogen gas at a pressure of 151.95 kPa and a temperature of 42oC, how
many grams of ammonia will you produce?
e. If the reaction in (d) actually produced 8.79g of ammonia, what is the percent yield?
UNIT VII REVIEW
2) Use the reaction in #1 to answer the following limiting reactant problem:
If you react 10.0 g of nitrogen with 3.00 g of hydrogen:
a) What is the limiting reactant? What is the excess reactant?
b) How many grams of ammonia should you get?
c) How many grams of the excess reactant will be left over?
3. Hydrogen cyanide is produced industrially from the reaction of gaseous ammonia, oxygen, and methane:
2 NH3 + 3 O2 + 2 CH4  2 HCN + 6 H2O
If 5.00 x 103 kg each of ammonia, oxygen, and methane are reacted, what mass of HCN and H2O would be
produced? (This is a limiting reactant problem)
UNIT VII REVIEW