CHM2046 Exam 1 February 2, 2006
Ticking away the moments that make up a dull day
You fritter and waste the hours in an off-hand way
Kicking around on a piece of ground in your home town
Waiting for someone or something to show you the way.
Please bubble in A, B or C as the test form code at the top right of your answer sheet.
For this version the correct answer to each question is a.
1. Once the reaction A + B C + D reaches equilibrium, there is no net change to the
concentrations of the species involved in the reaction because:
a. none of these.
b. the forward rate constant (k )fis equal to the backward rate constant (k ). b
c. reactions in both directions have stopped and nothing further can happen.
d. the forward and backward reaction rates are both zero.
e. not possible to decide without K . c
2. If the equilibrium constant, K, for a reaction A B is 1.0 x 10 , which of the following is
true at equilibrium?
a. [A] >> [B]
b. The reaction lies far to the right-hand side.
c. The forward reaction rate is much greater than the backward reaction rate.
d. All of the other four statements are wrong.
e. The K for B A is 1.0 x 10 .
3. Consider the reaction
H 2g) + I (2) 2 HI (g)
At a particular moment in time, [I ] i2 found to be increasing. Which of the following
statements is true at that moment?
a. Q c K c
b. Q c K c
c. Q c K c
d. Q c 0
e. cannot decide without knowing K . c
4. What is K foc the following reaction?
C2H 2g) + 3 H (g2 2 CH (4)
K c 3
a. [H 2 [C H 2 2
[C 2 ][2H ] 2 3
K c 2
5. At a particular temperature,
2 SO (2) 2 SO (g) + O (2) K c 1.8 x 10 -8
2 SO (g) 2 S (g) + O (g) K = 3.0 x 10 -10
Use the above information to calculate the K for che reaction below at that temperature.
2 SO (2) 2 S (g) + 2 O 2g) K c ?
a. 5.4 x 10
b. 3.3 x 10 -2
c. impossible to determine
e. 1.7 x 10 -2
6. K c 0.10 for the reaction below at a particular temperature.
2 SO 2g) + O (g2 2 SO 3g)
What is K foc the following reaction at the same temperature?
SO 3g) SO 2g) + 1/2 O (g)2
e. impossible to determine.
7. What is K foc the following reaction, whose K = 3.9 p 10 at 1000 K?
2 CO (g) C (s) + CO (g)
b. 3.9 x 10 -2
d. 4.8 x 10 -4
e. impossible to determine.
8. At a particular temperature, the following reaction has K = 24.cOne such reaction at
equilibrium has [H O]2= 1.6 M. What is the [H O ]? 2 2
2 H 2 (2) O 2g) + 2 H O2(g)
a. Impossible to determine
b. 0.29 M
c. 160 M
d. 0.64 M
e. 3.2 M 9. The reaction A + 2 B C + 2 D has K =c8. At a particular moment in time, [A] = [B] =
0.2 M, [C] = 0.6 M, and [D] = 0.8 M. Which of the following statements is true?
a. Q > K and the reaction is proceeding to the left.
b. Q < K and the reaction is proceeding to the right.
c. Q < K and the reaction is proceeding to the left.
d. Q > K and the reaction is proceeding to the right.
e. The reaction is at equilibrium.
10. The reaction 2 NH (g3 N 2g) + 3 H (2) has K = 9c0 at a particular temperature. At
equilibrium, [H ] = 0.32 M and [N ] = 0.10 M. What is [NH ] at equilibrium?
2 2 3
a. 1.9 x 10 M
b. 3.6 x 10 M
c. 2.8 x 10 M3
d. 2.6 x 10 M
e. cannot be determined without the temperature.
2 CO (g) + O (2) 2 CO 2g)
1.000 atm of CO and 1.000 atm of O were 2laced in a container, and the reaction allowed
to reach equilibrium. At equilibrium, P = 0.81 atm. What is K ?
e. impossible to determine
CO (2) + H (g2 CO (g) + H O2(g)
0.050 M CO and 0.100 M H were placed in a flask and allowed to reach equilibrium at a
particular temperature where K = 2c4. What is the [H ] at 2quilibrium?
a. 0.061 M
b. 0.011 M
c. 0.039 M
d. 0.094 M
e. none of the other answers
2 Cr2O 3s) 4 Cr (s) + 3 O 2g)
At a particular temperature, a vessel containing the above reaction at equilibrium was
found to contain P O2 = 0.24 atm. What is K atpthis temperature?
a. 0.014 M
b. 0.24 M
c. 0.058 M
d. 0.62 M
e. impossible to determine 14. In the following reaction, which has K = 3.2cx 10 and H = +1380 kJ, 1.0 mol of each
substance is introduced into a 1.0 L vessel in the presence of a catalyst and allowed to
reach equilibrium at a constant temperature.
2 CO (2) + 2 H O (g2 C 2 (4) + 3 O (g)2
If neon (Ne) gas is now added to the vessel, what will happen?
a. the equilibrium concentrations will stay the same.
b. [CO ]2will decrease and [C H ] w2ll4increase.
c. [CO ]2will increase and [C H ] 2il4 decrease.
d. all concentrations will increase.
e. all concentratio