Chapter 14 – Chemical Equilibrium
1. Which of the following statements is true in a reaction system at equilibrium?
A)
The equilibrium constant is zero.
B)
The number of collisions per unit time between reactants is equal to the number of
collisions per unit time between products.
C)
Reactants are reacting to form products at the same rate as products are reacting to
form reactants.
D)
Reactants and products are present in equimolar amounts.
E)
The product of the concentrations of the products divided by the product of the
concentrations of the reactants is always a constant.
2. When gaseous carbon monoxide and hydrogen are combined in a sealed vessel and heated
they will eventually form an equilbrium mixture of reactants and products according to the
balanced chemical equilibrium below.
CO(g) + 3H2(g)
CH4(g) + H2O(g)
In one such reaction 3 moles of one reactant were combined with 1 mole of the other
reactant in a fixed volume vessel and heated to 1200 K. Analysis of the reaction mixture at
various times gave the results below. Which component of the reaction mixture is
represented by curve B?
A)
carbon monoxide
B)
either methane or water
C)
hydrogen
D)
either hydrogen or carbon monoxide
E)
not enough information to decide
3. Which of the following represents a dynamic equilibrium?
A)
a stoppered flask half full of water
B)
a coin spinning in mid-air
C)
two people of equal mass balanced on the ends of a seesaw
D)
an open pan of boiling water
E)
an object traveling at a constant speed
4. Which of the following is/are true concerning a chemical reaction at equilibrium?
1.
2.
3.
A)
1 only
B)
2 only
C)
3 only
D)
1 and 2
E)
1, 2, and 3
5. A 15.00-L vessel at 700 K initially contains HI(g) at a pressure of 4.00 atm; at equilibrium,
it is found that the partial pressure of H2(g) is 0.387 atm. What is the partial pressure of
HI(g) at equilibrium?
2HI(g) H2(g) + I2(g)
A)
4.00 atm
B)
3.61 atm
C)
3.23 atm
D)
4.39 atm
E)
0.387 atm
6. Sulfur dioxide combines with O2 in the presence of a catalyst as represented by the equation
2SO2(g) + O2(g) 2SO3(g)
Suppose 0.10 mol of SO2 and 0.10 mol of O2 are added to a 1-L vessel. At equilibrium,
which of the following conditions must be true?
A)
[O2] = 2[SO3]
B)
[SO2] = [O2]
C)
[SO2] > [O2]
D)
[SO2] < [O2]
E)
[SO2] = [O2] = [SO3]
7. The Ostwald process converts ammonia (NH3) to nitric oxide (NO) by reaction with oxygen
in the presence of a catalyst at high temperatures. In a test of the process a reaction vessel is
initially charged with 3.90 mol NH3(g) and 4.90 mol O2(g), sealed, and heated at a fixed
high temperature. When equilibrium is established the reaction mixture is analyzed and
found to contain 2.90 mol NO(g). What is the quantity of NH3(g) in the equilibrium
reaction mixture?
4NH3(g) + 5O2(g) 4NO(g) + 6H2O(g)
A)
1.00 mol NH3(g)
B)
6.80 mol NH3(g)
C)
3.90 mol NH3(g)
D)
1.28 mol NH3(g)
E)
2.00 mol NH3(g)
8. The following reaction is investigated (assume an ideal gas mixture):
2N2O(g) + N2H4(g) 3N2(g) + 2H2O(g)
Initially there are 0.100 mol of N2O and 0.25 mol of N2H4, in a 10.0-L container. If there are
0.062 mol of N2O at equilibrium, how many moles of N2 are present at equilibrium?
A)
3.8 10–2
B)
1.1 10–1
C)
5.7 10–2
D)
1.9 10–2
E)
none of these
Test Bank General Chemistry, 10th edition 4
9. Apply the law of mass action to obtain the equilibrium-constant expression for the following
reaction:
2X(g) + Y(g) 3W(g) + V(g)
A)
[X]2[Y][W]3[V]
B)
C)
D)
10. Which of the following can we predict from an equilibrium constant for a reaction?
1.
2.
3.
A)
1 only
B)
3 only
C)
3 only
D)
1 and 2
E)
1 and 3
11. What is the expression for Kc for the following equilibrium?
CaCO3(s) CaO(s) + CO2(g)
A)
B)
C)
D)
E)
12. The reaction of a mixture of SO2 and O2 at a given temperature is represented by the
equation
2SO2(g) + O2(g) 2SO3(g)
When equilibrium is established, which of the following ratios is constant regardless of the
initial concentrations of SO2 and O2?
A)
B)
C)
D)
E)
13. What is the balanced equation for the following equilibrium expression?
A)
6SO2(g) + 3O2(g) 6SO3(g)
B)
6SO3(g) 6SO2(g) + 3O2(g)
C)
6SO3(aq) 6SO2(aq) + 3O2(aq)
D)
6SO2(aq) + 3O2(aq) 6SO3(aq)
E)
SO2(g) + O2(g) SO3(g)
Test Bank General Chemistry, 10th edition 6
14. What balanced equation is the following equilibrium expression derived from?
A)
1
3
H2(g) +
1
3
I2(g)
2
3
HI(g)
B)
2
3
HI(g)
1
3
H2(g) +
1
3
I2(g)
C)
1
3
H2(aq) +
1
3
I2(aq)
2
3
HI(aq)
D)
2
3
HI(aq)
1
3
H2(aq) +
1
3
I2(aq)
E)
2HI(g) H2(g) + I2(g)
15. Which of the following correctly describes the equilibrium constant for the gas-phase
reaction between H2 and O2 to form gaseous H2O?
A)
Kc =
B)
Kc =
C)
Kc = [H2O]
D)
Kc =
E)
Kc =
16. Which expression correctly describes the equilibrium constant Kc for the following reaction?
4NH3(g) + 5O2(g) 4NO(g) + 6H2O(g)
A)
B)
C)
D)
E)
17. Nitrogen trifluoride decomposes to form nitrogen and fluorine gases according to the
following equation:
2NF3(g) N2(g) + 3F2(g)
When 2.12 mol of NF3 is placed in a 5.00-L container and allowed to come to equilibrium at
800 K, the mixture is found to contain 0.0362 mol of N2. What is the value of Kp at this
temperature? (R = 0.0821 Latmmol-1K-1)
A)
1.07 10–5
B)
1.91 10–3
C)
1.78 10–3
D)
1.11 10–5
E)
4.43 10–7
18. For the reaction Br2(g) + Cl2(g) 2BrCl(g), at equilibrium, it is found that the
concentrations of Br2, Cl2, and BrCl are 0.398 M, 0.351 M, and 2.05 10–3 M, respectively.
What is the value of Kc?
A)
3.01 10–5
B)
1.20 10–4
C)
1.47 10–2
D)
6.81 101
E)
3.32 104
19. A sample of ammonia gas was allowed to come to equilibrium at 400 K.
2NH3(g) N2(g) + 3H2(g)
At equilibrium, it was found that the concentration of H2 was 0.0591 M, the concentration of
N2 was 0.0197 M, and the concentration of NH3 was 0.441 M. What is Kc for this
equilibrium?
A)
3.97 10–3
B)
1.58 10–5
C)
2.10 10–5
D)
2.24 10–1
E)
2.65 10–3
20. A 4.50-mol sample of HI is placed in a 1.00-L vessel at 460°C, and the reaction system is
allowed to come to equilibrium. The HI partially decomposes, forming 0.343 mol H2 and
0.343 mol I2 at equilibrium. What is the equilibrium constant Kc for the following reaction at
460°C?
½ H2(g) + ½ I2(g) HI(g)
A)
1.23 102
B)
8.10 10–3
C)
3.09 10–2
D)
11.1
E)
5.69
21. At 400 K, an equilibrium mixture of H2, I2, and HI consists of 0.065 mol H2, 0.079 mol I2,
and 0.13 mol HI in a 4.50-L flask. What is the value of Kp for the following equilibrium?
(R = 0.0821 L · atm/(K · mol))
2HI(g) H2(g) + I2(g)
A)
0.29
B)
8.2
C)
0.039
D)
26
E)
3.4
22. A sample of ammonia gas was allowed to come to equilibrium at 400 K.
2NH3(g) N2(g) + 3H2(g)
At equilibrium, it was found that the concentration of H2 was 0.0367 M, the concentration of
N2 was 0.0122 M, and the concentration of NH3 was 0.170 M. What was the initial
concentration of ammonia?
A)
0.122 M
B)
0.146 M
C)
0.218 M
D)
0.182 M
E)
0.194 M
23. A sample of ammonia gas was allowed to come to equilibrium at 400 K.
2NH3(g) N2(g) + 3H2(g)
At equilibrium, it was found that the concentration of H2 was 0.0283 M, the concentration of
N2 was 0.00944 M, and the concentration of NH3 was 0.101 M. What is Kp for this
equilibrium? (R = 0.0821 L · atm/(K · mol))
A)
4.28
B)
2.85
C)
1.70 10–2
D)
1.95 10–8
E)
2.26 10–2
24. For which of the following reactions are the numerical values of Kp and Kc the same?
1. 2SO2(g) + O2(g) 2SO3(g)
2. N2(g) + O2(g) 2NO(g)
3. H2(g) + I2(g) 2HI(g)
A)
1 only
B)
2 only
C)
1 and 2
D)
2 and 3
E)
1, 2, and 3
Test Bank General Chemistry, 10th edition 10
25. For the reaction 2NO(g) + O2(g) 2NO2(g) at 750°C, what is the relationship between
Kc and Kp?
A)
Kc = Kp
B)
Kc = Kp (RT)–1
C)
Kc = Kp = 1.0
D)
Kc = Kp (RT)¾
E)
Kc = Kp (RT)1
26. For which of the following equilibria does Kc = Kp?
A)
N2(g) + 3H2(g) 2NH3(g)
B)
CO(g) + H2O(g) CO2(g) + H2(g)
C)
CO(g) + 3H2(g) CH4(g) + H2O(g)
D)
CaO(s) + CO2(g) CaCO3(s)
E)
HBr(g) ½H2(g) + ½Br2(l)
27. If Kc = 0.145 for A2 + 2B 2AB, what is the value of Kc for the reaction
4AB 2A2 + 4B?
A)
0.145
B)
0.290
C)
47.6
D)
–0.145
E)
3.45
28. Consider the following equilibrium:
½N2O4(g) NO2(g); Kc = 3.3 at 100°C
For which of the following equilibria is Kc less than 3.3 at 100°C?
A)
¼N2O4(g) ½NO2(g)
B)
N2O4(g) 2NO2(g)
C)
4N2O4(g) 8NO2(g)
D)
3N2O4(g) 6NO2(g)
E)
2N2O4(g) 4NO2(g)
Test Bank General Chemistry, 10th edition 11
29. Carbon tetrachloride may react with oxygen to produce chlorine and carbonyl chloride.
2CCl4(g) + O2(g) 2COCl2(g) + 2Cl2(g); Kc = 9.9 1051
What is Kc for the following equilibrium?
COCl2(g) + Cl2(g) CCl4(g) + ½O2(g)
A)
9.9 10–51
B)
5.0 10–53
C)
1.0 10–26
D)
1.0 10–52
E)
–9.9 1051
30. At 298 K, the value of Kc for the reaction H2(g) + Br2(g) 2HBr(g) is 2.0 1019. What
is Kc for HBr(g) ½H2(g) + ½Br2(g)?
A)
4.0 10–38
B)
5.0 10–20
C)
1.0 1019
D)
–2.0 1019
E)
2.2 10–10
31. Given the equilibrium constants for the following reactions:
4Cu(s) + O2(g) 2Cu2O(s); K1
2CuO(s) Cu2O(s) + ½ O2(g); K2
What is K for the system
2Cu(s) + O2(g) 2CuO(s)
Test Bank General Chemistry, 10th edition 12
equivalent to?
A)
(K2)2/(K1)
B)
K1 K2
C)
(K1)(K2)½
D)
(K2)½/(K1)
E)
(K1)½/(K2)
32. Given the equilibrium constants for the equilibria,
2NH4+(aq) + 2H2O(l) 2NH3(aq) + 2H3O+(aq); Kc =
3.24 10−19
CH3COOH(aq) + H2O(l) CH3COO−(aq) + H3O+(aq); Kc =
1.75 10−5
determine Kc for the following equilibrium.
CH3COOH(aq) + NH3(aq) CH3COO−(aq) + NH4+(aq)
A)
3.08 104
B)
3.25 10-5
C)
9.96 10–15
D)
1.00 1014
E)
1.75 10-5
33. Determine Kc for reaction 3, given that reactions 1-3 may be rearranged and summed to give
reaction 4.
1. NH3(aq) + H2O(l) NH4+(aq) + OH−(aq); Kc = 1.76 x10-5
2. CH3COOH(aq) + H2O(l) CH3COO−(aq) + H3O+(aq); Kc = 1.75 x10-5
3. 4H2O(l) 2OH−(aq) + 2H3O+(aq); Kc = ?
4. CH3COOH(aq) + NH3(aq) CH3COO−(aq) + NH4+(aq); Kc = 3.08 x104
A)
9.36 10−20
B)
1.10 1010
C)
9.01 10−11
D)
1.00 10−28
E)
1.01 1014
34. What is the Kp equilibrium-constant expression for the following equilibrium?
Ti(s) + 2Cl2(g) TiCl4(l)
A)
B)
C)
D)
E)
35. What is the Kc equilibrium-constant expression for the following equilibrium?
S8(s) + 24F2(g) 8SF6(g)
A)
B)
C)
D)
E)
36. What is the Kp equilibrium-constant expression for the following equilibrium?
S8(s) + 24F2(g) 8SF6(g)
A)
B)
C)
D)
E)
37. What is the Kc equilibrium-constant expression for the following equilibrium?
FeO(s) + H2(g) Fe(s) + H2O(g)
A)
B)
C)
D)
E)
Test Bank General Chemistry, 10th edition 15
38. What is the Kc expression for the following equilibrium?
TlCl(s) Tl+(aq) + Cl−(aq)
A)
B)
C)
D)
E)
39. Consider the following equilibrium:
O2(g) + 2F2(g) 2OF2(g); Kp = 2.3 10–15
Which of the following statements is true?
A)
If the reaction mixture initially contains only OF2(g), then at equilibrium, the
reaction mixture will consist of essentially only O2(g) and F2(g).
B)
For this equilibrium, Kc = Kp.
C)
If the reaction mixture initially contains only OF2(g), then the total pressure at
equilibrium will be less than the total initial pressure.
D)
If the reaction mixture initially contains only O2(g) and F2(g), then at equilibrium,
the reaction mixture will consist of essentially only OF2(g).
E)
If the reaction mixture initially contains only O2(g) and F2(g), then the total
pressure at equilibrium will be greater than the total initial pressure.
40. For which of the following values of the equilibrium constant does the reaction mixture
contain mostly reactants?
A)
10
B)
10
C)
10−
D)
10–1
E)
10
41. For which of the following reactions will the reactant experience the largest degree of
decomposition upon reaching equilibrium at 500 K?
A)
2NO2F(g) 2NO2(g) + F2(g); Kp = 6.6 10–22
B)
2SO3(g) 2SO2(g) + O2(g); Kp = 1.3 10–5
C)
2NOF(g) 2NO(g) + F2(g); Kp = 1.2 10–26
D)
2NOCl(g) 2NO(g) + Cl2(g); Kp = 1.7 10–2
E)
2NO2(g) 2NO(g) + O2(g); Kp = 5.9 10–5
42. Which of the following is true for a system whose equilibrium constant is much greater than
one?
A)
The reaction mixture contains mostly products at equilibrium.
B)
The reaction mixture contains mostly reactants at equilibrium.
C)
The rate of reaction is very fast.
D)
The moles of reactants and products are relatively similar at equilibrium.
E)
Both A and C.
43. Which of the following can we determine by using an equilibrium constant for a gaseous
reaction system?
1.
2.
3.
A)
1 only
B)
2 only
C)
3 only
D)
1 and 2
E)
1, 2 and 3
44. Which of the following is always true for a reaction where Kc is
1.03 10−7
at 25C?
A)
The reaction mixture contains mostly reactants at equilibrium.
B)
The reaction mixture contains mostly products at equilibrium.
C)
The rate of reaction is very slow.
D)
There are approximately equal moles of reactants and products at equilibrium.
E)
Both A and C.
45. Which of the following is/are true concerning equilibrium constants?
1.
2.
3.
A)
1 only
B)
2 only
C)
3 only
D)
1 and 3
E)
1, 2, and 3
46. Consider the following reaction:
2HF(g) H2(g) + F2(g) (Kc = 1.00 10–2)
Given that 1.00 mol of HF(g), 0.371 mol of H2(g), and 0.750 mol of F2(g) are mixed in a
5.00-L flask, determine the reaction quotient, Q.
A)
Q = 0.0696
B)
Q = 0.278
C)
Q = 0.0557
D)
Q = 2.12
E)
none of these
Test Bank General Chemistry, 10th edition 18
47. Consider the following equilibrium:
C2H6(g) + C5H12(g) CH4(g) + C6H14(g); Kp = 9.57 at 500 K
Suppose 57.5 g each of CH4, C2H6, C5H12, and C6H14 are placed in a 10.0-L reaction vessel
at 500 K. What is the value of Qp?
A)
1.00
B)
0.104
C)
1.57
D)
0.637
E)
9.57
48. Consider the following equilibrium:
C2H6(g) + C5H12(g) CH4(g) + C6H14(g); Kp = 9.57 at 500 K
Suppose 47.2 g each of CH4, C2H6, C5H12, and C6H14 are placed in a 25.0-L reaction vessel
at 500 K. Which of the following statements is correct?
A)
Because Qc < Kc, more products will be formed.
B)
Because Qc = 1, the system is at equilibrium.
C)
Because Qc = 1, more products will be formed.
D)
Because Qc = 1, more reactants will be formed.
E)
Because Qc > Kc, more reactants will be formed.
49. For the reaction 2H2S(g) 2H2(g) + S2(g), Kc = 9.1 102 at 750 K. What will happen
when 0.10 mol of H2S, 1.0 mol of H2, and 1.5 mol of S2 are added to a 1.0-L container and
the system is brought to 750 K?
A)
More S2 will be formed than H2.
B)
More H2 will be formed than S2.
C)
Nothing; the system is at equilibrium.
D)
The amount of H2 formed will be half the amount of S2 formed.
E)
More H2S will be formed.