General Chemistry I
Writing & Balancing Chem.
Equations, Plus Conversions
Answers to Practice Problems
1. For the following, give the correctly
balanced chemical equation for:
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a. the reaction of silver
acetate with magnesium chloride to produce magnesium acetate and silver
chloride. 2 AgC2H3O2 +
MgCl2 ¾¾® 2 AgCl +
Mg(C2H3O2)2 |
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b. the reaction of calcium
oxide with tetraphosphorus decoxide
to produce calcium phosphate. 6 CaO + P4O10 ¾¾® 2 Ca3(PO4)2 |
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c. the reaction of aluminum sulfate with sodium
hydroxide to produce aluminum hydroxide and sodium sulfate. Al2(SO4)3 + 6 NaOH ¾¾® 2 Al(OH)3 + 3
Na2SO4 |
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d. the reaction of calcium hydroxide and hydrochloric
acid to produce calcium chloride and water. Ca(OH)2 + 2 HCl ¾¾® CaCl2 + 2
H2O |
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e. the complete combustion of C7H6O2. 2 C7H6O2 + 15
O2 ¾¾® 14
CO2 + 6 H2O |
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f. the reaction of nitrogen dioxide with water to
produce nitric acid and nitrogen monoxide. 3 NO2 + H2O ¾¾® 2 HNO3 + NO |
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g. the complete combustion of
butane, C4H10. 2 C4H10 + 13
O2 ¾¾® 8 CO2 + 10
H2O |
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h. the reaction of nitric acid with calcium hydroxide
to produce calcium nitrate and water. 2 HNO3 +
Ca(OH)2 ¾¾® Ca(NO3)2 + 2
H2O |
2. How many moles of nickel(II)
hydroxide are produced from the complete reaction of 2.5 moles of nickel(II)
chloride with excess sodium hydroxide?
(Sodium chloride is the other product.)
Moles NiCl2 ¾® Moles Ni(OH)2
2.5 moles nickel(II) hydroxide
3. How many grams of nickel(II)
hydroxide are produced from the reaction of 18.6 g of nickel(II) chloride with
excess sodium hydroxide? (Same chemical equation as above.)
Grams NiCl2 ¾® Moles NiCl2 ¾® Moles Ni(OH)2 ¾® Grams Ni(OH)2
13.3 grams nickel(II) hydroxide
4. Use the following
balanced chemical equation to answer the questions below.
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2 HNO3 +
Ca(OH)2 ¾¾® Ca(NO3)2 + 2
H2O |
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a. What mass, in grams, of calcium hydroxide is
required to react completely with 24.7 g of HNO3? Grams HNO3 ¾® Moles HNO3 ¾® Moles Ca(OH)2 ¾® Grams Ca(OH)2 14.5 grams calcium hydroxide |
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b. What mass, in grams, of calcium nitrate forms from
the complete reaction of 35.0 g of HNO3 with excess calcium
hydroxide? Grams HNO3 ¾® Moles HNO3 ¾® Moles Ca(NO3)2 ¾® Grams Ca(NO3)2 45.6 grams calcium nitrate |
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c. What is the percent yield of calcium nitrate if the
reaction of 43.5 g nitric acid with 28.3g of calcium hydroxide yields 48.2 g
of calcium nitrate? Grams HNO3 ¾® Moles HNO3 ¾® Moles Ca(NO3)2 ¾® Grams Ca(NO3)2 Grams Ca(OH)2 ¾® Moles Ca(OH)2 ¾® Moles Ca(NO3)2 ¾® Grams Ca(NO3)2 Nitric acid is limiting reagent, theoretical yield is 56.6 g, Percent yield = actual yield ÷ theoretical yield X 100 = 85.2% |
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5. Use the following
balanced chemical equation to answer the questions below.
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3 Mg + B2O3 ¾¾® 2 B
+ 3 MgO |
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a. How many grams of
magnesium are required to produce 11.4 g of boron? Grams B ¾® Moles B ¾® Moles Mg
¾® Grams Mg 38.5 g magnesium |
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b. What mass, in
grams, of B2O3 is required to completely react with 124.4
g of magnesium? Grams Mg ¾® Moles Mg
¾® Moles B2O3 ¾® Grams B2O3 118.8 grams B2O3 |
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c. How many grams of
boron are produced from the complete reaction of 87.3 g of magnesium with
excess B2O3? Grams Mg ¾® Moles Mg
¾® Moles B ¾® Grams B 25.9 grams boron |
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d. What is the maximum amount of boron that can be produced from
the reaction of 9.13 g of magnesium with 7.95 g B2O3? Grams Mg ¾® Moles Mg
¾® Moles B ¾® Grams B Grams B2O3
¾® Moles B2O3 ¾® Moles B ¾® Grams B 2.47 grams boron (This is also theoretical yield.) |
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e. The complete
reaction of 14.3 g of magnesium with 13.1 g B2O3
produces 19.8 g of magnesium oxide.
What are the limiting reactant, theoretical
yield, and percent yield? Grams Mg ¾® Moles Mg
¾® Moles MgO ¾® Grams MgO Grams B2O3
¾® Moles B2O3 ¾® Moles MgO ¾® Grams MgO B2O3 is limiting reagent, theoretical
yield is 22.8 g, percent yield is
86.8% |
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6. Propane, C3H8, is
combusted completely.
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a. Write and balance
the chemical equation for this reaction. C3H8 +
5 O2 ¾¾® 3 CO2 +
4 H2O |
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b. How many
molecules of propane are required to produce 25.8 g carbon dioxide in the
presence of excess oxygen? Grams CO2 ¾® Moles CO2 ¾® Moles C3H8 ¾® Molecules C3H8 1.18 x 1023
propane molecules |
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c. How many moles of
oxygen are required to completely react with 94.7 g propane? Grams C3H8
¾® Moles C3H8 ¾® Moles O2 10.7 moles oxygen |
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d. What is the maximum
amount, in grams, of water that can be formed from the complete reaction of
8.04 x 10-2 g propane with 9.83 x 10-2 g oxygen? Grams C3H8 ¾® Moles C3H8 ¾® Moles H2O ¾® Grams H2O Grams O2 ¾® Moles O2 ¾® Moles H2O ¾® Grams H2O 0.0442 grams water |
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e. The complete
reaction of 49.7 g oxygen with 14.6 g propane produces 38.0 g carbon
dioxide. What are
the limiting reagent, theoretical yield, and percent yield for this
reaction?
Grams C3H8
¾® Moles C3H8 ¾® Moles CO2 ¾® Grams CO2 oxygen is limiting reagent,
theoretical yield is 41.0 g,
percent yield is 92.7% |
7. Calculate the molarity
of a solution that contains 7.5 x 10-2 mole sodium sulfate in a
total of 250.0 mL of solution. 0.30 M
8. Calculate the molarity
of a solution made by dissolving 25.0 g sodium chloride in a total of 500.0 mL of water. 0.855 M
9. A solution is
prepared by dissolving 84.0 g potassium phosphate in a total of 1.5 L of
solution. The density of the solution is
1.23 g/mL.
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a. Calculate the molarity of the solution. 0.264 M |
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b. Calculate the
percent by mass of the solution. 4.55% |
10. Calculate the percent
by mass of a solution prepared by dissolving 1.8 x 10-3 mole of
magnesium chloride in 200.0 mL of aqueous
solution. The solution density is 1.02
g/mL. 0.084%
11. What mass, in grams,
of calcium chloride is required to prepare 750.0 mL
of a 5.0% solution? The solution density
is 1.18 g/mL.
44 grams calcium chloride
12. How many grams of copper(II)
sulfate are required to prepare 1.5 L of a 1.2 M solution? 2.9 x 102 grams copper(II) sulfate
13. How many mL of
ethyl alcohol (C2H5OH, D = 0.789 g/mL)
are required to prepare 500.0 mL of a 1.2 M solution
of ethyl alcohol? 35 mL
