General, Organic & Biological Chemistry, 5e (Timberlake)
Chapter 10 Reaction Rates and Chemical Equilibrium
10.1 Multiple Choice Questions
1) A catalyst is
A) a reactant in a chemical reaction.
B) a product in a chemical reaction.
C) a substance that speeds up a reaction without being consumed in the reaction.
D) a substance that increases the energy of the products.
E) a substance that decreases the energy of the products.
2) The activation energy of a chemical reaction is the energy that
A) must be removed from the mixture.
B) must be released from the mixture.
C) initiates the reaction.
D) activates the catalyst.
E) is the difference in the energies of the starting materials and products.
3) In a catalyzed chemical reaction, one function of a catalyst is to
A) increase the number of successful reactant collisions.
B) decrease the concentration of reactants.
C) change the equilibrium concentrations of the products and reactants.
D) increase the energy given off during the reaction.
E) increase the temperature at which the reaction is carried out.
4) The rate of any chemical reaction can be determined by observing
A) the amount of product formed in a unit of time.
B) the ratio of product concentration to reactant concentration.
C) the percent composition of the final product.
D) the theoretical yield of the reaction.
E) the number of chemical bonds broken and remade.
5) In any chemical reaction, the rate of the reaction can be increased by
A) decreasing the temperature.
B) changing the size of the container.
C) adding water to the reaction.
D) adding product molecules to the reaction mixture.
E) increasing the concentrations of the reactants.
6) Refrigerating perishable foods affects biochemical reactions by
A) increasing concentrations of antioxidants.
B) removing bacteria.
C) decreasing the rate of reactions affecting spoilage.
D) catalyzing the removal of harmful chemicals from the foods.
E) improving the appearance of the foods.
7) In a catalytic converter in an automobile, the reaction of carbon monoxide with oxygen produces
A) carbon dioxide.
B) carbon and more oxygen.
C) water.
D) methane.
E) nitrogen oxide.
8) One metal that is used as a catalyst in a catalytic converter in an automobile is
A) carbon.
B) iron.
C) copper.
D) platinum.
E) plutonium.
9) In the reaction of nitrogen and hydrogen to give ammonia, all the reactants and products are
A) gases.
B) liquids.
C) solids.
D) boiling.
E) frozen.
10) A reaction that can proceed in either the forward or the reverse direction as written is called a
________ reaction.
A) reversible
B) miniscule
C) microscopic
D) solid phase
E) favored
11) A chemical reaction has reached equilibrium when
A) the concentrations of reactants and products are equal.
B) all reactants have been converted to products.
C) all products have been removed from the reaction mixture.
D) the catalyst has been used up.
E) the rate of the forward reaction equals the rate of the reverse reaction.
12) When a reaction is at equilibrium,
A) all reaction stops.
B) no more reactants are converted to products.
C) the reaction is no longer reversible.
D) the forward and reverse reactions occur at the same rate.
E) the products and reactants have the same energy content.
13) The equation for the formation of ammonia from nitrogen and hydrogen is shown below. What is the
form of the equilibrium constant?
3H2(g) + N2(g) ⇌ 2NH3(g)
A)
B)
C)
D)
E)
14) The reaction for the decomposition of PCl5 to chlorine and PCl3 is shown below.
PCl5(g) ⇌ PCl3(g) + Cl2(g)
If the equilibrium concentrations are [PCl5] = 1.0 M, [PCl3] = 0.10 M, [Cl2] = 0.10 M, what is the value of
the equilibrium constant?
A) 1.0 × 10-2
B) 1.0 × 10-4
C) 10 × 10–2
D) 1.0 × 102
E) 2.0 × 10-2
15) What is the correct form for the equilibrium constant expression for this reaction?
H2(g) + F2(g) ⇌ 2HF(g)
A)
B)
C)
D)
E)
16) What is the correct form of the equilibrium constant for the reaction of hydrogen and oxygen to form
water? The equation is:
2H2(g) + O2(g) ⇌ H2O(g)
A) Kc =
B) Kc =
C) Kc =
D) Kc =
E) Kc =
17) An equilibrium in which all the components are gases is a ________ equilibrium.
A) heterogeneous
B) liquid
C) catalytic
D) homogeneous
E) reversible
18) For the following reaction, the equilibrium concentration of NO2 is 0.38 M and equilibrium
concentration of N2O4 is 1.0M. What is the value of the equilibrium constant?
2NO2(g) ⇌ N2O4(g)
A) 0.14
B) 2.6
C) 6.9
D) 0.38
E) 1.0
19) The equilibrium for the reaction for the decomposition of PCl5 to chlorine and PCl3 is 0.042.
PCl5(g) ⇌ PCl3(g)+ Cl2(g)
If the equilibrium concentrations are [PCl3] = 0.010 M, [Cl2] = 0.10 M, what is the value of [PCl5]?
A) 0.010 M
B) 0.0020 M
C) 0.042 M
D) 0.024 M
E) 0.0010 M
20) In the following gas phase reaction, Kc is much less than 1. At equilibrium, which of the following
statements is true?
COCl2(g) ⇌ CO(g) + Cl2(g)
A) The concentration of reactant is much greater than the concentration of products.
B) The concentration of products is much greater than the concentration of reactants.
C) The concentrations of products and reactants are approximately equal.
D) A catalyst will increase the concentration of products formed.
E) At equilibrium, the concentrations of reactants and products are equal.
21) The equilibrium constant for the production of carbon dioxide from carbon monoxide and oxygen is
Kc = 2 × 1011. This means that the reaction mixture at equilibrium is likely to consist of
A) mostly starting materials.
B) an equal mixture of products and reactants.
C) twice as much starting material as product.
D) twice as much product as starting material.
E) mostly products.
22) Which of the following equilibrium constants indicates the reaction that gives the smallest amount of
product?
A) Kc = 5 × 10–10
B) Kc = 5 × 10-1
C) Kc = 5 × 100
D) Kc = 5 × 101
E) Kc = 5 × 1010
23) The value of the equilibrium constant for the combination of nitrogen and oxygen to make NO is 2 ×
10-9. What does this tell you about the concentrations of materials in the equilibrium mixture?
A) The concentration of products exceeds the concentration of reactants.
B) The concentrations of reactants and products are equal.
C) The reactants are solids.
D) The concentration of reactants exceeds the concentration of products.
E) The products are solids.
24) Carbon monoxide binds to hemoglobin 140 times more strongly than oxygen does. What does this tell
you about the equilibrium constants for the two reactions of hemoglobin with carbon monoxide and
oxygen?
A) The equilibrium constant for the binding of CO is greater.
B) The equilibrium constant for the binding of oxygen is greater.
C) The concentration of carbon monoxide at equilibrium is twice that of oxygen.
D) Oxygen and carbon monoxide have the same formula mass.
E) Oxygen and carbon monoxide react with hemoglobin in different fashions.
25) For the following reaction, the equilibrium constant Kc is 2.0 at a certain temperature. If the
concentration of both products is 0.10 M at equilibrium, what is the concentration of the starting material,
NOBr?
2NOBr(g) ⇌ 2NO(g) + Br2(g)
A) 5 × 10–4 M
B) 2.2 × 10-4 M
C) 5 × 10-2 M
D) 2.2 × 10-2 M
E) 2.2 M
26) For the following reaction, the equilibrium constant Kc is 0.60 at a certain temperature. If the
concentration of NO(g) and NOBr(g) are both 0.50 M,at equilibrium, what is the concentration of Br2(g)?
2NO(g) + Br2(g) ⇌ 2NOBr(g)
A) 1.7 M
B) 0.60 M
C) 0.36 M
D) 2.8 M
E) 1.0 M
27) For the following equilibrium reaction, which cause and effect are correctly matched?
CO(g) + 2H2(g) ⇌ CH3OH(g) + heat
A) add heat, shift right
B) add CO, shift left
C) remove CH3OH, shift left
D) remove heat, no change
E) remove H2, shift left
28) In the following gas phase reaction, what is the effect of adding more NO2 to the starting reaction
mixture?
2NO2(g) ⇌ N2O4(g)
A) It would make the reaction more endothermic.
B) It would make the reaction more exothermic.
C) It would slow the reaction down.
D) It would decrease the final quantity of products.
E) It would increase the final quantity of products.
29) The physiological equilibrium system that keeps the temperature of the body constant is called
A) stimulation.
B) regulation.
C) metabolism.
D) homeostasis.
E) catalysis.
30) When you open a bottle of a soft drink and leave it open, the drink eventually goes flat. This happens
because the equilibrium between carbonic acid and carbon dioxide shifts to produce
A) more carbonic acid.
B) more water.
C) more oxygen.
D) more carbon dioxide.
E) more hydrogen ions.
31) Iron metal reacts with oxygen gas to produce iron(III) oxide. What will be the effect of increasing the
pressure of oxygen gas in a closed reaction vessel?
A) Less reaction will take place.
B) More iron oxide will be produced.
C) The reaction mixture will catch fire.
D) There is no effect; a catalyst is needed.
E) The rate of production of iron oxide will slow down.
32) In the following gas phase reaction, what is the effect on the direction of the reaction if more SO3 is
added to the reaction mixture?
2SO2(g) + O2(g) ⇌ 2SO3(g)
A) The equilibrium shifts to produce more products.
B) The position of the equilibrium remains unchanged.
C) The rate of formation of products is increased.
D) The equilibrium shifts to produce more reactants.
E) The catalyst for the reaction is used up.
33) In the reaction of nitrogen gas with oxygen gas to produce nitrogen oxide, what is the effect of adding
more oxygen gas to the initial reaction mixture? The reaction is shown below.
N2(g) + O2(g) ⇌ 2NO(g)
A) The equilibrium shifts to produce more N2.
B) The equilibrium shifts to produce more NO.
C) The equilibrium is not affected.
D) Extra catalyst is required to reach equilibrium.
E) The temperature of the reaction mixture is raised.
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34) The reaction of hemoglobin with oxygen can be written as follows.
Hb + O2 ⇌ HbO2
If the amount of oxygen available to the blood decreases significantly, what happens to the individual
involved?
A) Hypoxia results.
B) Anemia results.
C) Nitrogen narcosis results.
D) Oxygen poisoning results.
E) Acclimatization results.
35) N2(g) + O2(g) ⇌ 2NO(g)
For the reaction at equilibrium, if the volume of the container is decreased, the amount of NO present will
A) decrease.
B) increase.
C) double.
D) stay the same.
E) triple.
36) 2SO2(g) + O2(g) ⇌ 2SO3(g)
For the reaction at equilibrium, if O2 is added, the amount of SO2 present will
A) decrease.
B) increase.
C) stay the same.
37) PCl5 (g) ⇌ PCl3 (g)+ Cl2 (g)
For the reaction at equilibrium, if the volume of the container is increased, the amount of PCl5 present
will
A) decrease.
B) increase.
C) double.
D) stay the same.
E) triple.
38) Treatment of carbon monoxide poisoning can be accomplished by the use of pure oxygen for
breathing. This is an example of the use of ________ in a clinical setting.
A) the ideal gas law
B) Le Châtelier’s principle
C) Henry’s law
D) conservation of mass
E) a precipitation reaction
39) In the reaction of carbon dioxide with water to give carbonic acid, the only gaseous component is the
carbon dioxide. What will happen to the equilibrium concentration of carbonic acid if the pressure of
carbon dioxide is increased in the container?
A) The concentration of carbonic acid will increase.
B) The carbonic acid concentration will decrease.
C) The carbonic acid concentration will stay the same.
D) There will be twice as much carbonic acid as carbon dioxide.
E) There will be more water available for the reaction.
40) In an exothermic reaction, heat can be considered a
A) reactant.
B) product.
C) rate.
D) catalyst.
E) determinant.
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41) For the following reaction, the equilibrium constant Kc is 2.0 at a certain temperature. The reaction is
endothermic. What do you expect to happen to the concentration of NO if the temperature is doubled?
2NOBr(g) ⇌ 2NO(g) + Br2(g)
A) The concentration of NO will increase.
B) The concentration of NO will decrease.
C) There will be no change in [NO].
D) A catalyst will be needed to make a change in concentration.
E) The change in concentration of [NO] will depend on the size of the vessel.
42) For the following reaction, the equilibrium constant Kc is 2.0 at a certain temperature. Bromine can be
liquefied easily and removed from the reaction vessel as it is formed. If this is done, how will it affect the
equilibrium reaction?
2NOBr(g) ⇌ 2NO(g) + Br2(g)
A) More products will be made as Br2 is removed.
B) There will be a larger proportion NOBr in the vessel when equilibrium is reached.
C) Less NO will be made.
D) The pressure in the vessel will increase.
E) The equilibrium constant will change.
43) 3H2(g) + N2(g) ⇌ 2NH3(g) + heat
For the reaction at equilibrium, if the temperature is raised, the amount of N2 will
A) decrease.
B) increase.
C) stay the same.
10.2 Bimodal Questions
1) The ________ is the energy difference between reactants and products in a chemical reaction.
A) transition energy
B) activation energy
C) product energy
D) overall energy
E) heat of reaction
2) What is the correct form of the equilibrium constant for this reaction?
2H2O2 (g) ⇌ 2H2O (g) + O2 (g)
A)
B)
C)
D)
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3) For the following reaction, the equilibrium constant Kc is 2.0 at a certain temperature. Write the
equilibrium constant expression of the equilibrium constant, Kc.
2NOBr(g) ⇌ 2NO(g) + Br2(g)
A)
B)
C)
D)
E)
4) 2SO2(g) + O2(g) ⇌ 2SO3(g)
For the reaction at equilibrium, if O2 is removed, the amount of SO2 present will
A) decrease
B) increase
C) stay the same
10.3 Short Answer Questions
1) Write the equilibrium constant expression for the reaction of nitrogen and hydrogen to give ammonia,
NH3.
2) The equilibrium between hemoglobin and oxyhemoglobin in the blood can be represented by the
following reaction. Write the form of the equilibrium constant expression.
Hb + O2 ⇌ HbO2
3) A mixture at equilibrium that contains less product than reactant has a Kc that is ________ than 1.
4) An equilibrium constant with a value greater than 1 means the reaction favors the ________.
5) The rule or principle that describes the effect of changing reaction conditions on an equilibrium is
known as ________ principle.
10.4 True/False Questions
1) A catalyst lowers the activation energy of a chemical reaction.
2) Activation energy is always a large amount of energy.
3) The rate of a chemical reaction depends on temperature.
4) The rate of a chemical reaction is not affected by the concentration of reactants.
5) A catalyst for a chemical reaction affects the magnitude of the equilibrium constant.
6) One of the substances acted upon by a catalytic converter in an automobile is carbon dioxide.
7) At equilibrium, the concentrations of the reactants and products are always equal.
8) The equilibrium constant is the ratio of the concentrations of the reactants over the concentrations of
the products.
9) The equilibrium constant for the reaction of H2 and F2 to form HF, the concentration of HF is raised to
the second power.
10) An equilibrium constant Kc = 1 × 107 for a reaction indicates that the reaction favors product
formation.
11) An equilibrium constant greater than 1 for a reaction indicates that the reaction favors formation of
the products.
12) An equilibrium constant Kc = 1 × 10–3 for a reaction indicates that the reaction favors product
formation.
13) If the equilibrium constant for a reaction is 1 × 10-5, this means that the equilibrium mixture contains
mostly reactants.
14) The equilibrium constant for a reaction does not change with temperature.
15) An example of a stress on an equilibrium is the increase of pressure in a closed system when the
pressure of a reactant gas is increased from 1.0 atm to 2.0 atm.
10.5 Matching Questions
Indicate the effect of each change upon the rate of a reaction.
A) decreases
B) increases
1) adding a catalyst
Objective: 2.1
Global Outcomes: GO2
2) removing some reactant
Objective: 2.1
Global Outcomes: GO2
3) The temperature is doubled.
Objective: 2.1
Global Outcomes: GO2
4) The concentration of a reactant is decreased.
Objective: 2.1
Global Outcomes: GO2
5) More collisions between molecules occur.
Objective: 2.1
Global Outcomes: GO2