Chapter 18:
Chemical Equilibrium
Practice Test
1.
When Δ
G
is zero, _________.
a.
the reaction is spontaneous
b.
the reaction is not spontaneous
c.
the reaction is at equilibrium
d.
the reaction has no energy
Hint
2.
When the system A + B 3 C + D is at equilibrium, ___________.
a.
the forward reaction has stopped
b.
the reverse reaction has stopped
c.
both the forward and reverse reactions have stopped
d.
neither the forward nor the reverse reaction has stopped
Hint
3.
A molecular system that is a dynamic process with two opposing reactions balancing each other is a(n) ___________.
a.
chemical equilibrium
b.
spontaneous reaction
c.
nonspontaneous reaction
d.
unreacted set of chemicals
Hint
4.
What is the equilibrium constant expression for the following reaction?
4NH
3
(g) + 5O
2
(g) 3 4NO(g) + 6H
2
O(g)
a.
K
eq
= [NH
3
] [O
2
]/[NO] [H
2
O]
b.
K
eq
= [NH
3
]
4
[O
2
]
5
/[NO]<
4
[H
2
O]
6
c.
K
eq
= [NO]
4
/[NH
3
][O
2
]
d.
K
eq
= [NO]
4
[H
2
O]
6
/[NH
3
]
4
[O
2
]
5
Hint
5.
What is the equilibrium constant expression for the following reaction?
2NH
4
NO
3
(s) 3 2NH
3
(g) + 2NO(g) + H
2
(g) + 2O
2
(g)
a.
K
eq
= [NH
3
][NO][H
2
][O
2
]
b.
K
eq
= [NH
3
]
2
[NO]
2
[H
2
][O
2
]
2
c.
K
eq
= ([NH
3
][NO][H
2
][O
2
])/[NH
4
NO
3
]
d.
K
eq
v = ([NH
3
]
2
[NO]
2
[H
2
][O
2
]
2
)/[NH
4
NO
3
]
2
Hint
6.
What is the equilibrium constant expression for the following reaction in terms of the rate constants:
K
f
A + B ↔ C + D
K
r
a.
K
eq
=
K
f
b.
K
eq
v =
K
r
c.
K
eq
=
K
f
/
K
r
d.
K
eq
=
K
r
/
K
f
Hint
7.
For the reaction, 2A + B 3 C + 2D at 35°C, the value of the forward rate constant,
K
f
, is 3.0 × 10
-3
M
-1
s
-1
and the value of the reverse rate constant,
K
r
, is 1.5 × 10
-2
M
-2
s
-1
. Calculate the value of
K
eq
for this reaction.
a.
2
b.
0.5
c.
0.2
d.
5
Hint
8.
What is
K
eq
for the following reaction at equilibrium at a constant temperature if a 1—L vessel contains 0.10 mole of H
2
, 0.20 mole of N
2
, and 0.40 mole of NH
3
? N
2
(g) + 3H
2
(g) 3 2NH
3
(g)
a.
0.0012
b.
20
c.
8.0 × 10
2
d.
0.050
Hint
9.
Which of the following states that an equilibrium system that is disturbed will respond in a manner to restore equilibrium?
a.
Le Châtelier’s principle
b.
Boyle’s law
c.
Charles’s law
d.
Dalton’s law
Hint
10.
For the system, H
2
(g) + CO
2
(g) 3 H
2
O(g) + CO(g) at equilibrium, the addition of H
2
(g) would cause ____________.
a.
only more H
2
O to form
b.
only more CO to form
c.
more H
2
O and CO to form
d.
only more CO
2
to form
Hint
11.
For the reaction, 2SO
2
(g) + O
2
(g) 3 2SO
3
(g) at equilibrium, the removal of O
2
would cause _______________.
a.
the concentration of SO
2
to increase, and the concentration of SO
3
to increase
b.
the concentration of SO
2
to increase, and the concentration of SO
3
to decrease
c.
the concentration of SO
2
to decrease, and the concentration of SO
3
to increase
d.
the concentration of SO
2
to decrease, and the concentration of SO
3
to decrease
Hint
12.
For the reaction, 2SO
2
(g) + O
2
(g) 3 2SO
3
(g) at equilibrium, what will be the effect on the net amount of SO
3
present if the volume of the container is increased?
a.
The concentration of SO
3
will increase.
b.
The concentration of SO
3
will decrease.
c.
The concentration of SO
3
will remain the same.
d.
This question cannot be answered without knowing the value of
K
eq
.
Hint
13.
For the reaction, 2SO
2
(g) + O
2
(g) 3 2SO
3
(g) + heat, at equilibrium, what will be the effect on the net amount of SO
3
present if the temperature of the container is increased?
a.
The concentration of SO
3
increases.
b.
The concentration of SO
3
decreases.
c.
The concentration of SO
3
remains the same.
d.
This question cannot be answered without knowing the value of
K
eq
.
Hint
14.
For the gas phase reaction, SO
2
(g) +
O
2
(g) 3 SO
3
(g), Δ
H
° = -1.6 ×10
2
kJ for the forward reaction. To increase the yield of SO
3
, the reaction should be run at ________.
a.
high pressure and high temperature
b.
high pressure and low temperature
c.
low pressure and high temperature
d.
low pressure and low temperature
Hint
15.
Consider the following reaction in which all reactants and products are gases. 1.00 mole of A and 2.00 moles of B are placed in a 5.0-L container. After equilibrium has been established, 0.50 mole of D is present. What is the equilibrium constant for this reaction. A + 2B 3 2C + D
a.
1
b.
0.15
c.
0.33
d.
3
Hint
16.
For the reaction, H
2
(g) + Cl
2
(g) 3 2HCl(g) + heat, what will be the effect on the equilibrium constant,
K
eq
, if the pressure of the vessel is decreased at constant temperature?
a.
K
eq
increases
b.
K
eq
decreases
c.
K
eq
does not change
d.
The question cannot be answered without knowing the initial value of
K
eq
.
Hint
17.
For the reaction, 2NOCl(g) +75 kJ 3 2NO(g) + Cl
2
(g), which of the following will shift the reaction to the left?
a.
Add a catalyst.
b.
Heat the reaction vessel.
c.
Decrease the volume of the container.
d.
Add more NOCl.
Hint
18.
For the reaction, 2Cl
2
(g) + 2H
2
O(g) + heat 3 4HCl(g) + O
2
(g), which of the following will shift the equilibrium to produce more HCl?
a.
Add more Cl
2
.
b.
Lower the temperature of the reaction.
c.
Decrease the volume of the reaction vessel.
d.
Add more O
2
.
Hint
19.
When will the least time be required for a reaction to reach equilibrium?
a.
K
eq
is very small.
b.
K
eq
is very large.
c.
K
eq
is approximately 1.00.
d.
Cannot tell because the time to reach equilibrium does not depend on
K
eq
.
Hint
20.
Which of the following would force the forward reaction to completion?
CaCO
3
(s) + 2H
3
O
+
(aq) 3 Ca
2
+
(aq) + 3H
2
O(l) + CO
2
(g)
a.
Add base to neutralize the H
2
O
+
.
b.
Add more Ca
2+
to the mixture.
c.
Conduct the experiment in an open container.
d.
Add CO
2
to the mixture.
Hint
