Ch. 9 Review: Stoichiometry
1. The following equation represents a laboratory preparation for oxygen gas:
2KClO3(s) + heat 2KCl(s) + 3O2(g)
How many moles of O2 form as 3.0 mol of KClO3 are totally consumed?
2. Given the following equation: H2(g) + F2(g) 2HF(g), how many grams of HF gas are
produced as 5 mol of fluorine react?
3. Water can be made to decompose into its elements by using electricity according to the
following equation: 2H2O(l) + electrical energy 2H2(g) + O2(g)
How many grams of O2 are produced as 0.033 mol of water decompose?
4. Sodium metal reacts with water to produce NaOH according to the following equation:
2Na(s) + 2H2O(l) 2NaOH(aq) + H2(g)
How many grams of NaOH are produced if 20.0 g of sodium metal react with excess
1. Given the following equation: C3H4(g) + xO2(g) 3CO2(g) + 2H2O(g)
a. What is the value of the coefficient x in this equation?
b. What is the molar mass of C3H4?
c. What is the mole ratio of O2 to H2O in the above equation?
d. How many moles are in an 8.0 g sample of C3H4?
e. If z mol of C3H4 react, how many moles of CO2 are produced, in terms of z
2a. What is meant by “ideal conditions” relative to stoichiometric calculations?
b. What function do ideal stoichiometric calculations serve?
c. Are amounts actually produced typically larger or smaller than theoretic yields?
3. Assume the reaction represented by the following equation goes all the way to
completion. N2 + 3H2 2NH3
a. If 6 mol of H2 are consumed, how many moles of are NH3 produced?
b. How many grams are in a sample of NH3 that contains 3.0 X 1023 molecules?
9-3 Practice Problems
1. Identify the limiting reactant when 1.22 g of O2 reacts with 1.05 g of H2 to produce
2. Identify the limiting reactant when 4.68 g of Fe reacts with 2.99 g of S to produce FeS.
3. Identify the limiting reactant when 5.87 g of Mg(OH)2 reacts with 12.84 g of HCl to
form MgCl2 and water.
4. Identify the limiting reactant when 6.25 g of AgNO3 reacts with 4.12 g of NaCl to form
NaNO3 and AgCl.
5. Identify the limiting reactant when 7.81 g of HCl reacts with 5.25 g of NaOH to
produce NaCl and H2O.
6. Identify the limiting reactant when 6.33 g of H2SO4 reacts with 5.92 g of NaOH to
produce Na2SO4 and water.
7. Identify the limiting reactant when 43.25 g of CaC2 reacts with 33.71 g of water to
produce Ca(OH)2 and C2H2.
8. Identify the limiting reactant when 65.14 g of CaCl2 reacts with 74.68 g of Na2CO3 to
produce CaCO3 and NaCl
9. Identify the lmiting reactant when 4.687g of SF4 reacts with 6.281 g of I2O5 to produce
IF5 and SO2
10. If 4.1 g of Cr is heated with 9.3 g of Cl2, what mass CrCl3 will be produced?
11. What mass of SO2 is produced from the reaction between 31.5 g of S8 and 8.65 g of
12. What mass of SO3 is produced from the reaction of 12.4 g of SO2 and 3.45 g of O2?
13. What mass of H2SO4 is produced from the reaction of 6.58 g of SO3 and 1.645 g of
14. What mass of CdS is produced if 8.47 g of cadmium reacts with 2.51 g of sulfur?
Ch. 9 Review Problems
1. Nitrogen combines with oxygen in the atmosphere during lightning flashes to form
nitrogen monoxide, NO (30.01 g/mol), which then reacts further with O2 (32.00 g /mol)
to produce nitrogen dioxide, NO2 (46.01 g/mol)
a. What mass of NO2 is formed when NO reacts with 3.84 grams of O2?
b. How many grams of NO are required to react with this amount of O2?
2. Sulfuric acid (98.09 g/mol) reacts with aluminum hydroxide (78.01 g/mol) by double
replacement. 3H2SO4(aq) + 2Al(OH)3(s) Al2(SO4)3(aq) + 6H2O(l)
a. If 30.0 grams of sulfuric acid react with 25.09 grams of aluminum hydroxide,
identify the limiting reactant.
b. Determine the mass of excess reactant remaining
3. Methanol can be produced through the reaction of CO (28.01 g/mol) and H2 (2.02
g/mol) in the presence of a catalyst CO(g) + 2H2 (catalyst) CH3OH(l)
If 75.0 grams of CO reacts to produce 68.4 grams of CH3OH (32.05 g/mol), what is the
percent yield of CH3OH?
13. A sample of Calcium chloride (CaCl2) has a mass of 23.8 g. How many moles of
Calcium chloride is this?
14. How many grams are there in 0.36 moles of Cobalt (III) acetate (Co(C2H3O2)3)?
How many grams of cobalt are in this sample? How many atoms of cobalt?
15. How many mg of chlorine are there in a sample of 3.9 X 1019 molecules of chlorine
gas? How many atoms of chlorine?
16. Calculate the mass percent of each element in barium sulfate (BaSO3).
17. Calculate the mass percent of each element in natural leucite (KAlSi2O6).
18. Calculate the mass percent of silver (Ag) in each of the following compounds:
a. AgCl b. AgCN c. AgNO3
19. Chlorophyll a is essential for photosynthesis. It contains 2.72% magnesium (Mg) by
mass. What is the molecular weight of chlorophyll a assuming there is one atom of
magnesium in every molecule of chlorophyll a?
20. Which of the following formulas can be empirical?
a. CH4 b. CH2 c. KMnO4 d. N2O5 e. B2H6 f. NH4Cl g. Sb2S3 h. N2O4 i.
21. Determine the empirical and molecular formulas of a compound that weighs 31.04
g/mole and contains the following percentages of elements by weight:
C = 38.66 % H = 16.24% N = 45.10%
22. A compound is found, by mass spectra analysis, to contain the following percentages
of elements by weigh: C = 49.67% Cl = 48.92 % H = 1.39%
The molecular weight of the compound is 289.9 g/mole. Determine the empirical and
molecular formulas of the compound.
23. How many grams of product must be formed in each of the following reactions?
a. Two mole of H2 react with one mole of O2.
b. One mole of silver nitrate reacts with one mole of sodium chloride.
c. Three moles of sodium hydroxide react with one mole of phosphoric acid.
24. The following reaction was performed:
Fe2O3(s) + 2X(s) 2Fe(s) + X2O3(s)
It was found that 79.847 g of Fe2O3 reacted with “X” to form 55.847 g of Fe and 50.982 g
of X2O3. Identify element X.
25. Fill in the blanks to balance the following chemical equations.
a. _____AgI + _____Na2S _____Ag2S + _____NaI
b. _____(NH4)2Cr2O7 _____Cr2O3 + ____N2+_____H2O
c. _____Na3PO4 + _____HCl _____NaCl + _____H3PO4
d. _____TiCl4 + _____H2O _____TiO2 + _____HCl
e. _____Ba3N2 + _____H2O _____Ba(OH)2 + _____NH3
f. _____HNO2 _____HNO3 + _____NO + _____H2O
26. How many g of water vapor can be generated from the combustion of 18.74 g of
ethanol? C2H3O2(g) + O2 (g) CO2(g) + H2O(g) (unbalanced)
27. How many grams of sodium hydroxide are required to form 51.63 g of lead
hydroxide? Pb(NO3)2(aq + NaOH(aq) Pb(OH)2(s) + NaNO3(aq) (unbalanced)
28. How many grams of potassium iodide are necessary to completely react with 20.61 g
of Mercury (II) chloride? HgCl2(aq) + KI(aq) HgI2(s) + KCl(aq) (unbalanced)
29. A reaction combines 113.484 g of lead (II) nitrate with 45.010 g of sodium
hydroxide. (see problem 27)
a. How much lead (II) hydroxide is formed?
b. Which reagent is limiting? Which is in excess?
c. How much of the excess reagent is left over?
d. If the actual yield of lead (II) hydroxide was 80.02 g, what was the percent yield?
30. A reaction combines 64.81 g of silver nitrate with 92.67 g of potassium bromide.
AgNO3(aq) + KBr(aq) AgBr(s) + KNO3(aq)
a. How much silver bromide is formed?
b. Which reactant is limiting? Which is in excess?
c. How much of the excess reagent is left over?
d. If the actual yield of silver bromide was 14.77 g, what was the percent yield?