1
Introductory Chemistry, 5e (Tro)
Chapter 8 Quantities in Chemical Reactions
8.1 True/False Questions
1) Greenhouse gases affect the temperature of the earth by blocking sunlight from reaching earth.
2) Global warming is due to the greenhouse gases preventing heat from Earth escaping into
space.
3) The primary greenhouse gas is carbon dioxide.
4) The primary source for the rising carbon dioxide levels is respiration of the Earth’s growing
population.
5) One of the advantages of burning fossil fuels is that it produces O2 for humans to breathe.
6) Stoichiometry is a chemist’s version of following a recipe.
7) Given the recipe: 2 cups flour + 1 egg + 3 oz blueberries → 4 muffins.
You can make 9 muffins from 3.5 cups of flour.
8) Given the recipe: 2 cups flour + 1 egg + 3 oz blueberries → 4 muffins.
You can make 1 dozen muffins from 3 eggs.
9) If it takes 2 cups of milk and 1 cup of cocoa mix to make three servings of hot chocolate, and
you only have 1 cup of each, then you cannot make any hot chocolate.
10) Given the reaction: 2 Na(s) + Cl2(g) → 2 NaCl(s)
The conversion factor for chlorine gas to sodium metal is: 2 mol Cl ≡ 2 mol Na
11) Given the reaction: 2 Na(s) + Cl2(g) → 2 NaCl(s)
The conversion factor for chlorine gas to sodium chloride is: 1 mol Cl2 ≡ 2 mol NaCl
12) Given the chemical equation: 2 Ca + O2 → 2 CaO,
if 2 moles of CaO are formed in this reaction, then 2 moles of O2 must have reacted.
13) Before determining conversion factors, it is necessary to make sure the equation is properly
balanced.
14) The conversion factor between mass and moles for a compound is the molar mass.
15) The conversion factor for moles of carbon dioxide to mass of carbon dioxide is:
1 mole CO2 ≡ 44.01 g.
16) The limiting reactant is the reactant that produces the maximum amount of product.
17) The theoretical yield is the amount of each reactant needed in order to make the maximum
amount of product.
18) The limiting reactant is the product that is completely consumed in a chemical reaction.
19) The actual yield is the amount of product actually produced by a chemical reaction.
20) The percent yield is calculated by dividing the actual yield by the theoretical yield times 100.
21) Given the recipe: 2 cups flour + 1 egg + 3 oz blueberries → 4 muffins
If you have 5 cups of flour, 3 eggs and plenty of blueberries, the limiting reactant is the eggs.
22) Given the recipe: 2 cups flour + 1 egg + 3 oz blueberries → 4 muffins
If you have 9 cups of flour, 4 eggs and plenty of blueberries, the theoretical yield of muffins is
16.
23) The actual yield is the same as the theoretical yield if the reaction goes to completion and
there is no loss of product.
24) The limiting reactant determines what the actual yield is.
25) The limiting reactant is not necessarily the reactant with the least mass.
26) When viewing a chemical equation, the limiting reactant can never be a chemical on the
product side of the equation.
27) The percent yield can never be greater than 100%.
28) For the following reaction you have 8 grams of hydrogen and 2 grams of oxygen.
2H2 + O2 → 2H2O
The limiting reagent is the oxygen.
29) For the following reaction you have 8 grams of hydrogen and 2 grams of oxygen.
2H2 + O2 → 2H2O
The theoretical yield of the reaction is 4 grams of water.
30) For the following reaction you have 8 grams of hydrogen and 2 grams of oxygen.
2H2 + O2 → 2H2O
The excess reactant is the oxygen.
31) If the theoretical yield of a reaction is 144 grams and the actual yield of the reaction is 72
grams, the percent yield of the reaction is 200%.
32) The enthalpy of reaction, △H rxn, is the amount of thermal energy that flows when a
reaction occurs at constant temperature.
6
33) Thermal energy flows into the reaction and out of the surroundings in an endothermic
reaction.
34) An exothermic reaction has a negative enthalpy of reaction.
35) Since heat must be supplied to melt ice, the melting of ice is an endothermic process and so
has a positive enthalpy value.
36) Given the following generic equation, 2 A + 3B → A2B3 △H rxn = +444 kJ, if you
completely reacted 1 mole of compound A, the amount of heat absorbed would be 222 kJ.
8.2 Multiple Choice Questions
1) The average global temperature depends on all factors EXCEPT what?
A) the amount of incoming sunlight
B) the amount of outgoing heat lost to space
C) the amount of greenhouse gases
D) the angle of the earth’s surface in relation to the incoming sunlight
E) All of the above are factors.
2) Which of the below statements about global warming is FALSE?
A) Some greenhouses gases are needed to keep the proper temperature balance.
B) Greenhouse gases prevent heat from leaving the earth.
C) Greenhouse gases allow sunlight to reach and heat the earth.
D) If the level of greenhouse gases increases, the temperature will decrease.
E) none of the above
3) The primary cause of increasing greenhouse gases is:
A) the burning of vast amounts of rain forests.
B) the production of CO2 by respiration.
C) the increased use of natural gas, petroleum and coal.
D) the release of CO2 by decreasing solubility in the ocean.
E) none of the above
4) Which of the following is TRUE?
A) Stoichiometry shows the numerical relationship between chemical quantities in a balanced
chemical equation.
B) Stoichiometry allows prediction of the amounts of products that form in a chemical reaction
based on the amounts of reactants.
C) Stoichiometry allows prediction of how much of the reactants are necessary to form a given
amount of product.
D) All of the above are true.
E) None of the above are true.
5) How many waffles can be made from 1 dozen eggs, assuming you have enough of all other
ingredients?
Given: 2 cups flour + 3 eggs + 1 tbs oil → 4 waffles
A) 48
B) 12
C) 4
D) 16
E) not enough information
6) How many eggs are needed to make 1 dozen waffles, assuming you have enough of all other
ingredients?
Given: 2 cups flour + 3 eggs + 1 tbs oil → 4 waffles
A) 48
B) 9
C) 12
D) 16
E) not enough information
7) Diatomic N2 can react with diatomic H2 to form ammonia (NH3). The balanced chemical
equation is:
If 6 moles of H2 totally reacted with more than enough N2, how many moles of ammonia would
be expected to form?
A) 2 moles
B) 3 moles
C) 4 moles
D) 6 moles
E) not enough information
8) Diatomic O2 can react with the element magnesium to form magnesium oxide (MgO). The
balanced chemical equation is:
If 4 moles of magnesium totally reacted with more than enough O2, how many moles of MgO
would be expected to form?
A) 1 mole
B) 2 moles
C) 4 moles
D) 8 moles
E) not enough information
9) How many moles of water are made from complete reaction of 2.2 moles of oxygen gas with
hydrogen gas?
Given the reaction: 2H2 + O2 → 2H2O
A) 4.4
B) 1.1
C) 2.2
D) 3.3
E) not enough information
10) How many moles of water are made from complete reaction of 1.4 moles of hydrogen gas?
Given the reaction: 2H2 + O2 → 2H2O
A) 2.8
B) 0.7
C) 1.4
D) 2.1
E) not enough information
11) How many moles of H2 can be made from complete reaction of 3.0 moles of Al?
Given: 2 Al + 6 HCl → 2 AlCl3 + 3 H2
A) 3 moles
B) 3.0 moles
C) 4.5 moles
D) 9.0 moles
E) none of the above
12) How many moles of aluminum are needed to make 9 moles of molecular hydrogen?
Given the reaction: 2 Al + 6 HCl → 2 AlCl3 + 3H2
A) 2 moles
B) 3 moles
C) 4 moles
D) 6 moles
E) none of the above
13) How many moles of chlorine gas are needed to make 0.6 moles of sodium chloride?
Given the reaction: 2Na + Cl2 → 2NaCl
A) 0.6
B) 0.3
C) 1.2
D) 3.6
E) not enough information
11
14) How many moles of sodium metal are needed to make 3.6 moles of sodium chloride?
Given the reaction: 2Na + Cl2 → 2NaCl
A) 0.9
B) 7.2
C) 1.8
D) 3.6
E) not enough information
15) Suppose two chemical reactions are linked together in a way that the O2 produced in the first
reaction goes on to react completely with Mg to form MgO in the second reaction.
Reaction one: 2 KClO3 → 3 O2 + 2 KCl
Reaction two: 2 Mg + O2 → 2 MgO
If you start with 4 moles of KClO3, how many moles of MgO could eventually form?
A) 2 moles
B) 4 moles
C) 6 moles
D) 12 moles
E) none of the above
16) Given the balanced equation CH4 + 2 O2 → CO2 + 2 H2O, which of the following is NOT a
correct conversion factor?
A) 2 mole H2O = 18.02 g
B) 1 mole O2 = 32.00 g
C) 1 mole CH4 2 mole H2O
D) 2 mole O2 1 mole CO2
E) none of the above
17) How many grams of water are made from the reaction of 4.0 grams of hydrogen gas?
Given the reaction: 2H2 + O2 → 2H2O
A) 18
B) 72
C) 36
D) 4.5
E) not enough information
18) How many grams of water are made from the reaction of 16.0 grams of oxygen gas?
Given the reaction: 2H2 + O2 → 2H2O
A) 18
B) 9
C) 36
D) 16
E) not enough information
19) How many grams of chlorine gas are needed to make 117 grams of sodium chloride?
Given the reaction: 2Na + Cl2 → 2NaCl
A) 71.0
B) 142
C) 35.5
D) 48.2
E) not enough information
20) How many grams of sodium metal are needed to make 29.3 grams of sodium chloride?
Given the reaction: 2Na + Cl2 → 2NaCl
A) 46.0
B) 5.75
C) 23.0
D) 11.5
E) not enough information
21) Given that 4 NH3 + 5 O2 → 4 NO + 6 H2O, when 4.50 mol of H2O are formed, the amount
of NO formed is:
A) 1.50 mol.
B) 3.00 mol.
C) 4.50 mol.
D) 6.75 mol.
E) none of the above
22) Given that 4 NH3 + 5 O2 → 4 NO + 6 H2O, if 3.00 mol NH3 were made to react with
excess of oxygen gas, the amount of H2O formed would be:
A) 2.00 mol.
B) 3.00 mol.
C) 4.50 mol.
D) 6.00 mol.
E) none of the above
23) Iron metal reacts with oxygen to produce iron(III) oxide. If you have 12.0 moles of iron for
complete reaction, you need:
A) 9.0 moles of O2 and produce 3.0 moles of Fe2O3.
B) 12.0 moles of O2 and produce 24.0 moles of Fe2O3.
C) 9.0 moles of O2 and produce 6.0 moles of Fe2O3.
D) 4.5 moles of O2 and produce 3.0 moles of Fe2O3.
E) none of the above
24) Many metals react with halogens to give metal halides. For example,
2 Al (s) + 3 Cl2(g) → 2 AlCl3 (s)
If you begin with 13.5 g of aluminum:
A) you will need 23.6 g Cl2 for complete reaction and will produce 66.7 g of AlCl3.
B) you will need 53.2 g Cl2 for complete reaction and will produce 66.7 g of AlCl3.
C) you will need 26.6 g Cl2 for complete reaction and will produce 49.0 g of AlCl3.
D) you will need 11.8 g Cl2 for complete reaction and will produce 49.0 g of AlCl3.
E) none of the above
25) A chemist wishes to perform the following reaction: N2 + 3 H2 → 2 NH3
If only 14.0 g of N2 is available, what is the minimum amount, in grams, of H2 needed to
completely react with this quantity of N2?
A) 1.01 g
B) 1.51 g
C) 3.03 g
D) 6.06 g
E) none of the above
26) Which of the following statements is FALSE?
A) The limiting reactant is completely consumed in a chemical reaction.
B) The theoretical yield is the amount of product that can be made based on the amount of
limiting reagent.
C) The actual yield is the amount of product actually produced by a chemical reaction.
D) The percent yield = × 100%.
E) All of the above are true statements.
27) Which ingredient is the limiting reactant if you have 5 cups of flour, 9 eggs and 3 tbs of oil?
Given: 2 cups flour + 3 eggs + 1 tbs oil → 4 waffles
A) flour
B) eggs
C) oil
D) waffles
E) not enough information
28) What is the theoretical yield of waffles if you have 5 cups of flour, 9 eggs and 3 tbs of oil?
Given: 2 cups flour + 3 eggs + 1 tbs oil → 4 waffles
A) 10
B) 12
C) 6
D) 4
E) not enough information
29) Which ingredient is the limiting reactant if you have 6 cups of flour, 9 eggs and 2 tbs of oil?
Given: 2 cups flour + 3 eggs + 1 tbs oil → 4 waffles
A) flour
B) eggs
C) oil
D) waffles
E) not enough information
16
30) A tricycle factory uses the following items to produce one tricycle: 3 tires, 1 frame, and 2
pedals. If the factory has available 270 tires, 90 frames, and 170 pedals, which item would limit
the amount of complete tricycles that can be assembled?
A) tires
B) frames
C) pedals
D) both tires and frames are limiting
E) not enough information
31) What is the theoretical yield of waffles if you have 6 cups of flour, 9 eggs and 2 tbs of oil?
Given: 2 cups flour + 3 eggs + 1 tbs oil → 4 waffles
A) 10
B) 12
C) 8
D) 4
E) not enough information
32) Consider the following generic chemical equation: 2A + 5B → C + 3D
If you react 4 units of A with 10 units of B, which statement is TRUE?
A) Substance A will be the limiting reactant.
B) Substance B will be the limiting reactant.
C) There is just enough of A and B so that everything reacts completely.
D) Substance C cannot be formed from this reaction.
E) none of the above