Chemistry Name_____________________________________________Period____Date_____
Problem Solving
Stoichiometry
1. Ammonia is produced from nitrogen and hydrogen according to the reaction
N2(g) + 3H2 (g)

2NH3(g)
Write the six ratios of moles that can be derived from this equation.
2. The formation of aluminum oxide from its constituent elements is represented by the equation
4Al(s) + 3 O2(g)  2Al2O3
Write the six ratios of moles that can be derived from this equation.
3. Carbon disulfide is an important industrial solvent. It is prepared by the reaction of coke with
sulfur dioxide.
5 C(s) + 2 SO2(g)  CS2(l) + 4 CO(s)
Write the 12 ratios of moles that can be derived from this equation
4. Mole-Mole Problem. In a spacecraft, the carbon dioxide exhaled by astronauts can be
removed by its reaction with lithium hydroxide according to the following equation.
CO2(g) + 2 LiOH(s) 
Li2CO3(s) + H2O(l)
How many moles of lithium hydroxide are required to react with 20.0 moles of CO2, the
average amount exhaled by a person. (ans. 40.0 mol)
5. Mole-Mass Problem In photosynthesis, plants use energy from the sun to combine carbon
dioxide and water forming glucose and oxygen.
6CO2(g) + 6 H2O(l)  C6H12O6(aq) + 6O2(g)
(ans. 90.0g)
How many grams of glucose is produced when 3.00 moles of water react with carbon dioxide?
6. Mass-Mole Problem. The industrial solvent carbon disulfide is produced through the
Following reaction between coke and sulfur dioxide.
C(s) + SO2(g)  CS2(l) + CO(g)
(ans. .0624 mol CS2 , .250 mol CO)
If 8.00g of SO2 reacts, (a) how many moles of Cs2 are formed? (b) how many moles of CO?
7. Mass-Mass Problem. Tin(II) fluoride, or stannous fluoride, is added to some home dental
treatment products. It is made y the reaction of tin with hydrogen fluoride.
Sn(s) + 2HF(g)  SnF2(s) + H2(g)
How many grams of SnF are produced from the reaction of 30.00g of HF with Sn?
Mole-Mole Calculations
8. Ammonia is produced from nitrogen and hydrogen. N2(g) + 3H2(g)  2NH3(g)
a) Calculate the number of moles of nitrogen required to make 7.4 moles of ammonia.
b) Calculate the number of moles of nitrogen needed to react with 5.64 moles of hydrogen to
produce ammonia.
c) How many moles of hydrogen are needed to produce 6.23 moles of ammonia?
9. The formation of aluminum oxide is represented by 4Al(s) + 3O2(g)  2Al2)3(s)
a) How many moles of aluminum are needed to form 2.3 moles of Al2O3?
b) How many moles of oxygen are required to react completely with 0.48 mole of Al?
c) Calculate the number of moles of Al2O3 formed when 17.2 mol of O2 react with aluminum.
Mass-Mole and Mole-Mass Calculations
10. When magnesium burns in air, it combines with oxygen to form magnesium oxide.
2Mg(s) + O2(g)  2MgO(s)
a) What mass of Mg is needed to react with 1.75 mol of oxygen?
b) What mass of magnesium is needed to produce 3.5 mol of magnesium oxide?
11. Oxygen was discovered by Joseph Priestly in 1774 when he decomposed mercury (II) oxide
its constituent elements by heating it. 2 HgO(s)  2 Hg(l) + O2(g)
a) How many moles of mercury(II) oxide (HgO) are needed to produce 125g of oxygen (O2)?
b) How many moles of mercury are produced in the above reaction?
12. Potassium chlorate will form potassium chloride and oxygen when heated according to the
reaction: 2KClO3(s)  2KCl(s) + 3O2(g)
How many moles of oxygen will be produced by 60.4 grams of potassium chlorate?
13. Iron combines with oxygen when it is heated to form iron(III) oxide. How many grams of
Iron(III) oxide will form from 3.00 mol of iron? 4Fe(s) + 3 O2(g)  2 Fe2O3(s)
Mass-Mass Calculations
14. Tin reacts with hydrogen fluoride to form tin(II) fluoride. Sn(s) + 2HF(g)  SnF2(s) + H2(g)
a. If 45.00g of SN react with HF, how many grams of HF are needed?
b. During the above reaction, 45.0g of hydrogen gas were produced. How many grams of
SnF2 were also produced?
15. Laughing gas(nitrous oxide – N2O) is sometimes used as an anesthetic in dental work. It is
produced when ammonium nitrate is decomposed. NH4NO3(s)  N2O(g) + 2H2O(l)
a. How many graom of NH4NO3 are required to produce 33.0g of N2O?
b. How many grams of water are produced in this reaction?
16. Methane reacts with chlorine gas to form methyl chloride and hydrogen chloride.
CH4(g) + Cl2(g)  CH3Cl(g) + HCl(g)
a. How many grams of methane are needed to produce 85.0g of methyl chloride?
b. How many grams of chlorine are needed to react with 75.9g of methane?
Mixed Problem Types – Calculations
17. Acetylene gas (C2H2) is produced by adding water to calcium carbide (CaC2).
CaC2(s) + 2H2O(l)  C2H2(g) + Ca(OH)2(aq)
a. How many grams of acetylene are produced by adding water to 5.00 g of CaC2?
b. How many moles of CaC2 are needed to react completely with 98.0g of H2O?
c. How many grams of Ca(OH)2 are produced when 5.34 mol of C2H2 are produced?
18. Ammonia (NH3) is widely used as a fertilizer and in may household cleaners. How many
moles of ammonia are produced when 6.0 mol of hydrogen gas react with an excess of
nitrogen gas? N2(g) + 3H2(g)  2NH3(g)
19. Methanol (CH3OH) is used in the production of many chemicals. Methanol is made by
reacting carbon monoxide with hydrogen at high temperature and pressure.
CO(g) + 2H2(g)  C2H2OH(l)
a. How many moles of CO are needed to form 6.00 x 102 g of CH3OH?
b. How many grams of hydrogen are necessary to react with 5.74 mol of CO?
Limiting Reactant
20. For each of these balanced equations, identify the limiting reagent for the given combination
of reactants.
a.
2H2 + O2
5.0 mol
b.
4P
+
d.
2Al
2H2O

O2
7.0 mol
c.

2.3 mol
2P2O5
8.0 mol
+ 3Cl2

5.4 mol
8.0 mol
2P2O5
+ 6H2O
0.37 mol
2 AlCl3

4H3PO4
2.50 mol
21. Acetylene (C2H2) will combine with oxygen. 2C2H2(g) + 5O2(g)  4CO2(g) + 2H2O(l)
a. How many moles of water can be produced by the reaction of 4.80 mol of C2H2 with
14.8 mol of O2? (Hint: first determine the limiting reactant)
b. How many grams of water can be produced?
22. Sodium chloride can be prepared by the reaction of sodium metal with chlorine gas.
2Na(s) + Cl2(g)  2NaCl(s) If 6.70 mol Na react with 3.20 mol of Cl2 thena. What is the limiting reactant?
What is the excess reactant?
b. How many moles of NaCl are produced?
c. How much of the excess reactant will remain?
23. Copper reacts with sulfur to form copper(I) sulfide. 2Cu(s) + S(s)  Cu2S(s)
a. What is the limiting reactant when 80.0g of Cu react with 25.0g of S?
b. How many grams of Cu2 can be formed in this reaction?
24. Hydrogen gas can be produced I the laboratory by the reaction of magnesium metal with
Hydrochloric acid. Mg(s) + 2HCl(aq)  MgCl2(aq) + H2(g)
a. How many moles of hydrogen will form when 4.00g of HCl and 3.00g of Mg combine?
b. How many grams of hydrogen will be produced?
c. How much of the excess reactant did react?
Percent Yield Calculations
25. The actual amount of product in a reaction is 39.7g. A mass-mass calculation predicts that
65.5g should be produced. What is the percent yield?
26. N2(g) + 3H2(g)  2NH3(g) If 5.50g of hydrogen reacts with nitrogen to form 20.4g
of ammonia thena. What is the actual yield?
b. What is the theoretical yield?
c. What is the percent yield?
27. A student should recover 21.8g of a product from a reaction. However, only 13.9g resulted.
a. What is the actual yield?
b. What is the theoretical yield?
c. What is the percent yield?
∆
28. Calcium carbonate can be decomposed by heating. CaCO3(s)  CaO(s) + CO2(g)
What is the percent yield if 24.8g of calcium carbonate is heated to give 13.1 g of
calcium oxide?
29. What is the percent yield if 3.74g of copper is produced when 1.87g of aluminum is
reacted with an excess of copper(II) sulfate?
2 Al(s) + 3 CuSO4(aq)  Al2(SO4)(aq) + 3Cu(s)
30. When 84.8g of iron(III) oxide reacts with an excess of carbon monoxide, then 57.8g of
iron is produced. What is the percent yield for this reaction?
Fe2O3(s) + CO(g)  2Fe(s) + 3CO2(g)
31. When 50.0g of silicon dioxide is heated with an excess of carbon, 32.2g of silicon carbide
are produced. What is the percent yield?
SiO2(s) + 3C(s)  SiC(s) + 2CO(g)
32. Calculate the actual yield given the percent yield and the theoretical yield.
Percent Yield
a. 89.0%
Theoretical Yield
230.0g
Actual yield
__________________g
b. 73.0%
6.50g
__________________g
c. 95.0%
36.0g
___________________g