76) The enthalpy for the following reaction is 136 kJ. If the reaction takes place in a closed container,
which one of the following reaction conditions will not decrease the concentration of water vapor?
2 NaHCO3(s) ⇌ Na2CO3(s) + CO2(g) + H2O(g)
A) add CO2
B) cool the container
C) decrease the volume of the container
D) remove some NaHCO3
77) A crude type of disappearing ink is based on the following endothermic equilibrium:
[Co(H2O)6]Cl2 (aq) ⇌ [CoCl2(H2O)4] (aq) + 2 H2O (l)
(colorless) (blue)
If the reactant solution is used to write on a piece of paper and the paper is allowed to partially dry, what
can be done to bring out the colored handwriting?
A) add water
B) decrease the volume
C) put the paper in a freezer
D) put the paper in an oven
78) For the reaction shown below, which change in conditions made to the system at equilibrium will
result in a net reaction to the right to form more product?
C(s) + 2 H2(g) ⇌ CH4(g) ΔH° = – 74.8 kJ
A) adding He
B) adding more C
C) decreasing the volume
D) increasing the volume
79) Which change in the system will drive equilibrium to the left in the reaction below?
N2O5(g) ⇌ NO2(g) + NO3(g)
A) decrease the amount of NO3
B) increase the amount of N2O5
C) increase the pressure
D) increase the volume
80) Ammonium bromide is a crystalline solid that decomposes endothermically when heated:
NH4Br(s) ⇌ NH3(g) + HBr(g). When solid NH4Br is added to an evacuated flask at 300°C, which
change in reaction conditions below will cause the equilibrium to shift to the right?
A) add more NH3
B) add more NH4Br
C) decrease the temperature
D) double the volume of the container
81) For the reaction shown below, which change in conditions made to the system at equilibrium will
result in a net reaction to the right to form more product?
C(s) + 2 H2(g) ⇌ CH4(g) ΔH° = –74.8 kJ
A) adding more C
B) increasing the volume
C) lowering the temperature
D) raising the temperature
82) What effect will a change in temperature have on the value of Kp?
A) It will have no effect on the value of Kp.
B) The value of Kp always decreases with an increase in temperature.
C) The value of Kp always increases with an increase in temperature.
D) The value of Kp will decrease or increase with an increase in temperature, depending on whether the
reaction is exothermic or endothermic.
83) The overall reaction for photosynthesis can be represented by the following equation:
6 CO2(g) + 6 H2O(l) ⇌ C6H12O6(s) + 6 O2(g)
The enthalpy change for this reaction is 2802 kJ. Which of the following changes in condition will shift
the equilibrium to the right?
A) increase the pressure of O2
B) increase the temperature
C) remove CO2 by reaction with CaO(s)
D) remove one-half of C6H12O6(s)
84) The dissolution of calcium hydroxide is exothermic.
Ca(OH)2(s) ⇌ Ca2+(aq) + 2 OH–(aq) What happens when the solution of Ca(OH)2 is heated?
A) The amount of Ca(OH)2(s) decreases.
B) The amount of Ca(OH)2(s) increases.
C) The amount of Ca(OH)2(s) remains unchanged.
D) The Ca(OH)2(s) completely dissolves.
85) Calcium carbonate is relatively insoluble and the dissolution reaction is endothermic:
CaCO3(s) ⇌ Ca2+(aq) + CO32-(aq). Which change in reaction condition below will shift the
equilibrium to the right?
A) add an acid to react with CO32- ion
B) add an anion with which Ca2+ is even less soluble than calcium carbonate
C) increase the temperature
D) All of these will shift reaction to the right.
86) The decomposition of nitrosyl bromide is exothermic: 2 NOBr(g) ⇌ 2 NO(g) + Br2(g). Which of the
following changes in reaction condition will shift the reaction to the left?
A) add more NOBr
B) decrease the temperature
C) increase the container volume
D) None of these
87) Which will not alter the composition of an equilibrium mixture?
A) addition of a catalyst
B) addition of heat
C) addition of more product
D) addition of more reactant
88) Which of the following changes in reaction conditions will not alter the composition of a
homogeneous equilibrium mixture of gases in a reaction having unequal moles of gaseous products and
reactants?
A) addition of a catalyst
B) addition of reactants or products
C) decreasing the temperature
D) increasing the pressure or volume
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89) Which of the following statements about a catalyst is true?
A) A catalyst changes the position of the equilibrium in a reaction.
B) A catalyst increases the temperature of a reaction.
C) A catalyst is consumed in a chemical reaction.
D) A catalyst provides a lower energy pathway for a reaction.
90) A catalyst increases the overall rate of reaction by lowering the activation energy, Ea, for
A) both the forward reaction and the reverse reaction.
B) neither the forward reaction nor the reverse reaction.
C) only the forward reaction.
D) only the reverse reaction.
91) A catalyst increases the rate of a chemical reaction by providing a lower-energy mechanism for the
reaction. When this occurs, which one of the following is not affected?
A) activation energy for the forward reaction
B) activation energy for the reverse reaction
C) equilibrium constant
D) rate of the reverse reaction
92) A reaction reaches dynamic equilibrium at a given temperature when
A) the amount of products exceeds the amount of reactants.
B) kfwd equals krev.
C) opposing reactions cease and the system is static.
D) the relative amounts of reactants and products are constant and ratefwd = raterev.
93) Find the equilibrium constant for the reaction: A(g) + B(g) ⇌ 2C(g) at 25°C when k equals 1.4 × 10–
12 M-1s-1 for the reaction A(g) + B(g) ⇌ 2C(g) at 25°C and k equals 2.7 × 10-13 M-1s-1 for the
reaction: 2 C(g) ⇌ A(g) + B(g) at 25°C.
A) 3.8 × 10-25
B) 1.7 × 10-12
C) 1.1 × 10-12
D) 5.2
94) At 25°C, a certain first order reaction has a rate constant equal to 1.00 × 10-3 s-1 and an equilibrium
constant, Kc, equal to 4.18. What is the rate constant for the reverse reaction?
A) 2.39 × 10-4 s-1
B) 4.18 × 10-3 s-1
C) 2.39 × 102 s-1
D) 4.18 × 103 s-1
95) Nickel metal can be prepared by the reduction of nickel oxide:
NiO(s) + CO(g) ⇌ CO2(g) + Ni(s)
At 936 K, Kp = 4.54 × 103 and at 1125 K, Kp = 1.58 × 103. Which statement is true?
A) The activation energy decreases with increasing temperature.
B) The activation energy increases with increasing temperature.
C) The reaction is endothermic.
D) The reaction is exothermic.
96) The hexaammine cobalt(III) ion is very unstable in acidic aqueous solution:
[Co(NH3)6]3+(aq) + 6 H3O+(aq) → [Co(H2O)6]4+(aq) + 6 NH4+(aq)
However, solutions of hexaammine cobalt(III) can be stored in acidic solution for months without
noticeable decomposition. Which statement below about the equilibrium constant and the activation
energy for the reaction is true?
A) Keq < 103 and Ea is very small.
B) Keq > 103 and Ea is very small.
C) Keq < 103 and Ea is very large.
D) Keq > 103 and Ea is very large.
97) The reaction below virtually goes to completion because cyanide ion forms very stable complexes
with Ni2+ ion:
[Ni(H2O)6]2+(aq) + 4 CN–(aq) → [Ni(CN)4]2-(aq) + 6 H2O(l)
At the same time, incorporation of 14C labelled cyanide ion (14CN–) is very rapid:
[Ni(CN)4]2-(aq) + 4 14CN–(aq) = [Ni(14CN)4]2-(aq) + 4 CN–(aq)
Which statement below is correct with regard to stability and rate of reaction?
A) Equilibrium is static.
B) Stable species can react rapidly.
C) Stable species do not react rapidly.
D) Unstable species react rapidly.
Consider the interconversion of A molecules (shaded spheres) and B molecules (unshaded spheres)
according to the reaction A ⇌ B. Each of the following series of pictures represents a separate
experiment in which time increases from left to right.
98) Which of these experiments has resulted in an equilibrium state?
A) all of the experiments except experiment (1)
B) all of the experiments except experiment (2)
C) all of the experiments except experiment (3)
D) all of the experiments except experiment (4)
99) What is the value of the equilibrium constant Kc for the reaction A ⇌ B?
A) Kc = 0.33
B) Kc = 3.0
C) Kc = 12
D) Kc = 27
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The following pictures represent the equilibrium state for four different reactions of the type
A2 + X2 ⇌ 2 AX (X = B, C, D, E). A atoms are unshaded. X atoms are shaded.
100) Which reaction has the largest equilibrium constant?
A) A2 + B2 ⇌ 2 AB
B) A2 + C2 ⇌ 2 AC
C) A2 + D2 ⇌ 2 AD
D) A2 + E2 ⇌2 AE
101) Which reaction has the smallest equilibrium constant?
A) A2 + B2 ⇌ 2 AB
B) A2 + C2 ⇌ 2 AC
C) A2 + D2 ⇌ 2 AD
D) A2 + E2 ⇌ 2 AE
102) The reaction A2 + B2 ⇌ 2 AB has an equilibrium constant Kc = 1.8. The following pictures
represent reaction mixtures that contain A2 molecules (shaded) and B2 molecules (unshaded), and AB
molecules. Which reaction mixture is at equilibrium?
A) reaction mixture (1)
B) reaction mixture (2)
C) reaction mixture (3)
D) reaction mixture (4)
103) The following pictures represent mixtures of cis-C2H2X2 molecules and trans-C2H2X2
molecules, which interconvert according to the equation cis-C2H2X2 ⇌ trans-C2H2X2. If mixture (1) is
at equilibrium, which of the other mixtures are also at equilibrium?
A) mixture (2)
B) mixture (3)
C) mixture (4)
D) None of the other mixtures are at equilibrium.
104) The following pictures represent mixtures of cis-C2H2X2 molecules and trans-C2H2X2
molecules, which interconvert according to the equation cis-C2H2X2 ⇌ trans-C2H2X2. If mixture (1) is
at equilibrium, which of the other mixtures are also at equilibrium?
A) mixture (2)
B) mixture (3)
C) mixture (4)
D) None of the other mixtures are at equilibrium.
105) The following pictures represent mixtures of A2B4 molecules and AB2 molecules, which
interconvert according to the equation A2B4 ⇌ 2 AB2. If mixture (1) is at equilibrium, which of the
other mixtures are also at equilibrium?
A) mixture (2)
B) mixture (3)
C) mixture (4)
D) None of the other mixtures are at equilibrium.
106) The following pictures represent mixtures of A2B4 molecules and AB2 molecules, which
interconvert according to the equation A2B4 ⇌ 2 AB2. If mixture (1) is at equilibrium, which of the
other mixtures are also at equilibrium?
A) mixture (2)
B) mixture (3)
C) mixture (4)
D) None of the other mixtures are at equilibrium.
107) Shown below is a concentration vs. time plot for the reaction A ⇌ B. For this reaction the value of
the equilibrium constant is
A) Kc < 1.
B) Kc = 0.
C) Kc = 1.
D) Kc > 1.
108) Shown below is a concentration vs. time plot for the reaction A ⇌ 2B. For this reaction the value of
the equilibrium constant is
A) Kc < 1.
B) Kc = 0.
C) Kc = 1.
D) Kc > 1.
109) Shown below is a concentration vs. time plot for the reaction A ⇌ B. For this reaction the value of
the equilibrium constant is
A) Kc < 1.
B) Kc = 0.
C) Kc = 1.
D) Kc > 1.
110) Shown below is a concentration vs. time plot for the reaction A ⇌ 2B. For this reaction the value of
the equilibrium constant is
A) Kc < 1.
B) Kc = 0.
C) Kc = 1.
D) Kc > 1.
111) Shown below is a concentration vs. time plot for the reaction A ⇌ B. For this reaction the value of
the equilibrium constant is
A) Kc < 1.
B) Kc = 0.
C) Kc = 1.
D) Kc > 1.
112) Shown below is a concentration vs. time plot for the reaction A ⇌ 2B. For this reaction the value of
the equilibrium constant is
A) Kc < 1.
B) Kc = 0.
C) Kc = 1.
D) Kc > 1.
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113) The following picture represents the equilibrium state for the reaction A2 + B2 ⇌ 2AB. What is the
relationship between the rate constant for the forward reaction, kf, and the rate constant for the reverse
reaction kr?
A) kf < kr
B) kf = kr = 0
C) kf = kr
D) kf > kr
114) The following picture represents the equilibrium state for the reaction A2 + B2 ⇌ 2AB. What is the
relationship between the rate constant for the forward reaction, kf, and the rate constant for the reverse
reaction kr?
A) kf < kr
B) kf = kr = 0
C) kf = kr
D) kf > kr