Chapter 11-12 Review Sheet – Stoichiometry
P.S. 11.1
• Mole Concept (Mole wheel problems)
Atomic mass/ molar mass (molecular weight)
Avogadro’s number
Molar Volume
Mole conversions (mass  moles, volume  moles, # particles  moles)
P.S. 11.2
• Determining empirical formulas (from % mass, grams, or moles)
• Determining molecular formulas
• formulas of hydrates
P.S. 12.1 & P.S. 12.2
• 3-step mole method problems!!!!
• Balancing equations
• diatomic molecules
P.S. 12.3
• limiting reagent
• percent yield
• theoretical yield
Expt. S-3 & Expt. #7
• Determining balanced equations from experimental data
• Law of conservation of mass
• error analysis
• % yield and % error
PRACTICE PROBLEMS
1) Complete the following:
a. What’s the mass of 20.0 L of CO2 at STP?
b. How many molecules would be contained in 45.0 L of N2O gas at STP?
c. What’s the mass of 8.34 x 1024 molecules of diphosphorus pentoxide, P2O5?
d. How much space would 35.0 grams of sulfur hexafluoride, SF6, occupy at STP?
e. What’s the mass of 3.56 x 1024 formula units of sodium sulfide, Na2S?
f. How many grams of iron in 2.35 x 1054 atoms?
g. How many moles of CO2 are needed to fill a 52.9 L box? How many grams of gas would be in the box?
2) Calculate the molar mass of the following (remember to round to the tenths place).
Ca(OH)2
H2O
CO2
Cl2
O
O2
3) Complete the following:
a. How many atoms of carbon are in 42.8 grams of sucrose, C12H22O11?
b. How many atoms of oxygen are needed to form two molecules of hydrogen peroxide – H2O2?
c. How many moles of oxygen atoms are needed to form two moles of hydrogen peroxide molecules – H2O2?
d. How many atoms of hydrogen in 50.0 grams of isopropanol, C3H7OH?
e. How many atoms of oxygen would be need to make 0.750 moles of dinitrogen tetroxide, N2O4?
4) Determine the empirical formula for the following compounds:
a. A sample contains 40.0% C, 6.67% H, and 53.3% O.
b. A sample contains 12.3 g C and 2.72 g H.
c. A sample contains 0.267 mol C, 0.667 mol H, and 0.133 mol O.
5) Determine the molecular formula for each of the compounds in (14) given the following molar masses:
a. 147 g/mol
b. 88.0 g/mol
c. 90.0 g/mol
6) A 10.0 gram sample of hydrated zinc nitrate, Zn(NO3)2 • X H2O is heated. The mass after heating was found to be
6.37 grams. What’s the formula of the hydrated compound?
7) A 10.0 gram sample of copper (II) nitrate trihydrate, Cu(NO3)2 • X H2O, is heated. What would be the mass of the
solid after heating?
8) Elements A and B are both diatomic. One mole of A reacts with one mole of B to produce two moles of C. What
must be the formula of C in terms of A and B?
9) Element D is monatomic. Element E is diatomic. Four moles of D react with one mole of E to produce two moles
of F. What must be the formula of F in terms of D and E?
10) 2.14 grams of methane, CH4, are combusted. How many grams of water should be produced?
11) 4.25 grams of magnesium metal is placed in a solution of copper (II) nitrate, Cu(NO3)2. The reaction produces
copper metal and magnesium nitrate, Mg(NO3)2.
a. How many grams of copper metal should be produced?
b. If 10.51 grams of copper are produced, what’s your percent error?
12) 5.00 grams of lead (II) nitrate, Pb(NO3)2, are dissolved in solution, then reacted with excess potassium chromate,
K2CrO4. Solid lead (II) chromate and aqueous potassium nitrate, KNO3 are produced. How many grams of solid
precipitate should form?
13) 40.0 L of CO2 are produced when a sample of propane is combusted. How many grams of propane must have been
burned?
C3H8 (g) + 5 O2 (g)  3 CO2 (g) + 4 H2O (l)
14) How many grams of chlorine gas are needed to completely react with 3.50 grams of potassium?
2 K(s) + Cl2 (g)  2 KCl (s)
15) How many molecules of hydrogen are needed to react with excess oxygen to form 89.0 grams of water vapor?
2 H2 + O2  2 H2O
16) For the following questions, consider the balanced equation below:
2 C4H10 + 13 O2 ---> 8 CO2 + 10 H2O
a. How many moles of O2 will be needed to burn 0.500 moles of C4H10?
b. What mass is this amount of O2?
c. How many grams of CO2 will be formed?
d. How many molecules of H2O will be formed?
17) One mole of a phosphorus oxide, P?O?, decomposes into 2 moles of phosphorus and 2 moles of oxygen, O2. What
is the formula for the phosphorus oxide?
18) For the following questions, consider the balanced equation below.
N2 + 3 H2 ---> 2NH3
a. If 3.00 moles of N2 are mixed with 3.00 moles of H2, which is the limiting reagent?
b. How many moles of NH3 will be formed?
c. What’s the mass of this amount of NH3?
d. What’s your excess reagent? _________ How many moles will be left over? ________
19) Using the equation below, calculate the following:
N2 + 3 H2 ---> 2NH3
a. If you mix 28 grams of N2 and 20 grams of H2, which is the limiting reagent?
b. How many grams of ammonia should be formed?
c. If you only formed 32.5 grams of ammonia, what is your percent yield? (refer to your answer to 19b)
20) 24.8 grams of propane, C3H8, react with 20.0 grams of oxygen to form carbon dioxide and water.
C3H8 + 5 O2  3 CO2 + 4 H2O
a. What is the limiting reagent?
b. What is the excess reagent?
c. How much of the excess reagent remains unreacted?
d. How many grams of each product are formed?
21) 78.5 g. of sulfuric acid are reacted with 35.8 g. of iron (III) hydroxide, Fe(OH)3. How many grams of iron sulfate,
Fe2 (SO4)3, are formed?
2 Fe(OH)3 + 3 H2 SO4  Fe2 (SO4)3 + 6 H2O