The following pictures represent the initial state and the equilibrium state for the gaseous state reaction of
A2 molecules (shaded spheres) with B atoms (unshaded spheres) to give AB molecules.
96) What is the best balanced chemical equation for the reaction?
A) A2 + B ⇌ A2B
B) A2 + 2 B ⇌ A2B2
C) A2 + 2 B ⇌ 2 AB
D) 6 A2 + 9 B ⇌ 3 A2 + 3B + 6 AB
97) If the volume of the equilibrium mixture is decreased, what will happen to the number of AB
molecules and the number of B atoms?
A) The number of AB molecules and the number of B atoms will both decrease.
B) The number of AB molecules will increase; the number of B atoms will decrease.
C) The number of AB molecules will decrease; the number of B atoms will increase.
D) The number of AB molecules and the number of B atoms will both increase.
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Consider the reaction A + B ⇌ 2 AB. The vessel on the right contains an equilibrium mixture of A atoms
(shaded spheres), B atoms (unshaded spheres), and AB molecules.
98) If the barrier between the two vessels is removed and the contents of the two vessels are allowed to
mix, what will be observed?
A) The reaction will go in the forward direction decreasing the number of A atoms and B atoms and
increasing the number of AB molecules.
B) The reaction will go in the forward direction increasing the number of A atoms and B atoms and
decreasing the number of AB molecules.
C) The reaction will go in the reverse direction decreasing the number of A atoms and B atoms and
increasing the number of AB molecules.
D) The reaction will go in the reverse direction increasing the number of A atoms and B atoms and
decreasing the number of AB molecules.
Picture (1) represents the equilibrium mixture for the reaction A + B ⇌ 2 AB at 298 K.
99) If this reaction is exothermic, which picture (2)-(4) represents the equilibrium mixture at 400 K?
A) picture (2)
B) picture (3)
C) picture (4)
D) None of these
100) If this reaction is endothermic, which picture (2)–(4) represents the equilibrium mixture at 400 K?
43
A) picture (2)
B) picture (3)
C) picture (4)
D) None of these
101) Picture (1) represents the equilibrium mixture for the gas-phase reaction A + B ⇌ 2 AB at 298 K. If the
volume of the equilibrium mixture is decreased, which picture (2)-(4) represents the equilibrium at the
reduced volume?
A) picture (2)
B) picture (3)
C) picture (4)
D) None of these
Picture (1) represents an equilibrium mixture of solid CaCO3, solid CaO, and gaseous CO2, obtained as a
result of the endothermic decomposition of CaCO3.
102) Which picture (2)-(4) represents the equilibrium mixture after addition of four more CO2 molecules?
A) picture (2)
B) picture (3)
C) picture (4)
D) None of these
103) Which picture (2)-(4) represents the equilibrium mixture at a higher temperature?
A) picture (2)
B) picture (3)
C) picture (4)
D) None of these
104) Which picture (2)-(4) represents the equilibrium mixture when a catalyst is added?
A) picture (2)
B) picture (3)
C) picture (4)
D) All of these
105) Which picture (2)-(4) represents the equilibrium mixture when more solid CaCO3 is added?
A) picture (2)
B) picture (3)
C) picture (4)
D) All of these
106) Which picture (2)-(4) represents the equilibrium mixture when more solid CaO is added?
A) picture (2)
B) picture (3)
C) picture (4)
D) All of these
14.2 Algorithmic Questions
1) For the reaction: N2(g) + 2 O2(g) ⇌ 2 NO2(g), Kc = 8.3 × 10–10 at 25°C. What is the concentration of N2
gas at equilibrium when the concentration of NO2 is twice the concentration of O2 gas?
A) 2.1 × 10–10 M
B) 4.2 × 10–10 M
C) 2.4 × 109 M
D) 4.8 × 109 M
2) Write the equilibrium equation for the forward reaction:
4 CH4 (g) + 6 O2 (g) ⇌ 4 CO (g) + 8 H2O (g)
A) Kc =
B) Kc =
C) Kc =
D) Kc =
3) Write the equilibrium equation for the reverse reaction:
4 CH4 (g) + 6 O2 (g) ⇌ 4 CO (g) + 8 H2O (g)
A) Kc‘ =
B) Kc‘ =
C) Kc‘ =
D) Kc‘ =
4) Nitric oxide reacts with oxygen to form nitrogen dioxide:
2 NO(g) + O2(g) ⇌ 2 NO2(g)
What is Kc for the forward reaction if the equilibrium concentration of NO is 0.200 M, O2 is 0.100 M, and
NO2 is 0.200 M at 25°C?
A) 35
B) 0.200
C) 0.10
D) 10.0
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5) If Kc equals 0.110 at 25°C for the reaction: N2O4(g) ⇌ 2 NO2(g), what is Kc for the reaction: 6NO2(g) ⇌
3 N2O4(g)?
A) 1.3 × 10-3
B) 751
C) 7.5
D) 0.11
6) The decomposition of ammonia is: 2 NH3(g) = N2(g) + 3 H2(g). If Kp is 1.5 × 103 at 400°C, what is the
partial pressure of ammonia at equilibrium when N2 is 0.40 atm and H2 is 0.15 atm?
A) 9.0 × 10-7 atm
B) 9.5 × 10-4 atm
C) 1.1 × 103 atm
D) 1.1 × 106 atm
7) The decomposition of ammonia is: 2 NH3(g) ⇌ N2(g) + 3 H2(g). If the partial pressure of ammonia is
1.60 × 10-3 atm and the partial pressures of N2 and H2 are each 0.250 atm at equilibrium, what is the
value for Kc at 400°C for the forward reaction?
A) 0.500
B) 1.00
C) 1.53 × 103
D) 6.53 × 10-4
8) Which equilibrium below is homogeneous?
A) CaSO4(s) ⇌ Ca2+(aq) + SO42-(aq)
B) 2 H2O2(l) ⇌ 2 H2O(l) + O2(g)
C) NH4NO3(s) ⇌ N2O(g) + 2 H2O(g)
D) 2 CO(g) + O2(g) ⇌ 2 CO2(g)
9) For which one of the following reactions will Kc = Kp?
A) CO(g) + 2 H2(g) ⇌ CH3OH(g)
B) NiO(s) + CO(g) ⇌ Ni(s) + CO2(g)
C) 2 O3(g) ⇌ 3 O2(g)
D) COF2(g) ⇌ CO(g) + F2(g)
10) If Kc = 0.600, and Kp = 359 for a hypothetical reaction, which of the equations below could represent
the reaction at 25°C?
A) 4 A(g) + B(s) ⇌ 6 C(g)
B) A(l) + 2 B(g) ⇌ 2 C(g)
C) B(g) ⇌ C(l) + D(l)
D) A(g) ⇌ 2 C(s) + D(g)
11) At some temperature, a 4.0 L flask is found to contain 10.0 mol of CO2, 8.0 mol of C, and 10.0 mol of
CO, at equilibrium. What is the value of the equilibrium constant, Kc, for this reaction?
A) 1.25
B) 0.50
C) 0.40
D) 2.50
12) Kc is 1.67 × 1020 at 25°C for the formation of iron(III) oxalate complex ion:
Fe3+(aq) + 3 C2O42-(aq) ⇌ [Fe(C2O4)3]3-(aq).
If 0.0400 M Fe3+ is initially mixed with 1.00 M oxalate ion, what is the concentration of Fe3+ ion at
equilibrium?
A) 3.51 × 10–22 M
B) 0.0100 M
C) 4.18 × 1017 M
D) 2.85 × 1021 M
13) The equilibrium constant is equal to 5.00 at 1300 K for the reaction:
2 SO2(g) + O2(g) ⇌ 2 SO3(g).
If initial concentrations are [SO2] = 3.60 M, [O2] = 0.45 M, and [SO3] = 5.40 M, the system is
A) at equilibrium.
B) not at equilibrium and will remain in an unequilibrated state.
C) not at equilibrium and will shift to the left to achieve an equilibrium state.
D) not at equilibrium and will shift to the right to achieve an equilibrium state.
14) The equilibrium constant, Kp, equals 3.40 at 25°C for the isomerization reaction:
cis-2-butene ⇌ trans-2-butene.
If a flask initially contains 3.00 atm of each gas, in what direction will the system shift to reach
equilibrium?
A) It will shift left.
B) It will shift right.
C) The system is already at equilibrium.
D) The system is not at equilibrium and will remain in an unequilibrated state.
15) Cyclohexane (C6H12) undergoes a molecular rearrangement in the presence of AlCl3 to form
methylcyclopentane (MCP) according to the equation:
C6H12 ⇌ MCP
If Kc = 0.143 at 25°C for this reaction, predict the direction in which the system will shift if the initial
concentrations of C6H12 and MCP are 0.800 M and 0.400 M, respectively. The system
A) will shift left.
B) will shift right.
C) is already at equilibrium.
D) is not at equilibrium and will remain in an unequilibrated state.
16) At a certain temperature, hydrogen and iodine react to form hydrogen iodide:
H2(g) + I2(g) ⇌ 2 HI (g).
When initial amounts of H2, I2, and HI are mixed, the concentration of HI increases. Which statement
below is true?
A) Kc < Q
B) Kc > Q
C) Kc = Q
D) More information is needed to make a statement about Kc.
17) An equilibrium mixture of CO, O2 and CO2 at a certain temperature contains 0.0010 M CO2 and
0.0020 M O2. At this temperature, Kc equals 1.4 × 102 for the reaction:
2 CO(g) + O2(g) ⇌ 2 CO2(g).
What is the equilibrium concentration of CO?
A) 3.6 × 10-6 M
B) 1.9 × 10-3 M
C) 7.0 × 10–2 M
D) 2.6 × 10-1 M
18) At a certain temperature, Kc equals 1.4 × 102 for the reaction:
2 CO(g) + O2(g) ⇌ 2 CO2(g).
If a 5.00-L flask contains 0.400 mol of CO2 and 0.100 mol of O2 at equilibrium, how many moles of CO are
also present in the flask?
A) 1.20 mol
B) 0.239 mol
C) 0.107 mol
D) 0.0114 mol
19) For the isomerization reaction:
butane ⇌ isobutane
Kp equals 25 at 500°C. If the initial pressures of butane and isobutane are 10. atm and 0.0 atm,
respectively, what are the pressures of the two gases at equilibrium?
A) P(butane) = 0.38 atm and P(isobutane) = 9.6 atm
B) P(butane) = 0.40 atm and P(isobutane) = 10. atm
C) P(butane) = 9.6 atm and P(isobutane) = 0.38 atm
D) P(butane) = 10 atm and P(isobutane) = 0.40 atm
20) Cyclohexane, C6H12, undergoes a molecular rearrangement in the presence of AlCl3 to form
methylcyclopentane, CH3C5H9, according to the equation:
C6H12 ⇌ CH3C5H9
If Kc = 0.143 at 25°C for this reaction, find the equilibrium concentrations of C6H12 and CH3C5H9 if the
initial concentrations are 0.200 M and 0.200 M, respectively.
A) [C6H12] = 0.150 M, [CH3C5H9] = 0.150 M
B) [C6H12] = 0.050 M, [CH3C5H9] = 0.162 M
C) [C6H12] = 0.350 M, [CH3C5H9] = 0.050 M
D) [C6H12] = 0.396 M, [CH3C5H9] = 0.004 M
21) At a certain temperature the equilibrium constant, Kc, equals 0.11 for the reaction:
2 ICl(g) ⇌ I2(g) + Cl2(g).
What is the equilibrium concentration of ICl if 0.65 mol of I2 and 0.65 mol of Cl2 are initially mixed in a
2.0-L flask?
A) 0.20 M
B) 0.24 M
C) 0.39 M
D) 0.49 M