102 HOMEWORK 2
SAMPLE QUESTIONS FOR CHAPTER 14
1. Consider the reaction
Ag3PO4(s) <===> 3Ag+(aq) + PO43-(aq)
The equilibrium constant expression for this reaction is
a
[Ag 3 PO 4 ]
. Kc =
[Ag + ][ PO 34- ]
b
[Ag PO ]
3
4
. Kc =
[Ag + ]3 [PO 34- ]
c
[Ag + ][PO 34- ]
. Kc =
[Ag 3 PO 4 ]
d
[Ag + ]3 [PO 34- ]
K
=
. c
[Ag 3 PO 4 ]
e
.
[
K = Ag +
c
] [PO ]
3
34
ANS: E
2. Chemical equilibrium exists in a reaction mixture when
a. reactants are completely changed to products.
b. there are equal concentrations of reactants and products.
c. the rate at which reactants form products becomes zero.
d. the concentrations of both products and reactants do not change.
e.
the concentrations of both products and reactants do not change.
Ans: e. the concentrations of both products and reactants do not change.
3. Consider the reactions
2NO + O2 <===> 2 NO2
K=a
2 NO2
<===> N2O4
K=b
The value of the equilibrium constant for the reaction
4NO + 2O2 <===> 2N2O4 is
a a+b
.
b ab
.
c (a/b)2
.
d (ab)2
.
e ab/2
.
ANS: D. (ab)2
4. Consider the reaction
COCl2(g) <===> CO(g) + Cl2(g), with Kc = 2.73  10-10
In a system where the original concentration of COCl2 was 0.0627 M, calculate the equilibrium
concentrations of CO and Cl2.
a 2.30  108 M
.
b 1.52  104 M
.
c 2.03  10-3 M
.
d 4.14  10-6 M
.
e 1.71  10-11 M
.
ANS:
D. 4.14  10-6 M
5. Consider the reaction system:
2N2(g) + O2(g)  2N2O(g)
Kc = 1.5  10-30
At equilibrium, the concentration of N2 was measured as 0.048 M and the concentration of O 2 as
0.093 M. What is the concentration of N2O in this system?
a 8.2 
.
10-17
b 1.8 
.
10-17
c 4.7 
.
10-27
d 3.4 
.
10-28
e 3.2 
.
10-34
ANS: B. 1.8  10-17
6. When 1.50 moles of A and 2.00 moles of B are placed in a 5.00 L flask and allowed to come to
equilibrium,
there are 0.920 moles of C in the mixture. Calculate the concentration of B at equilibrium.
2 A + 3 B <==> 2 C
a. 0.223 M
b. 0.124 M
c. 0.103 M
d. 0.620 M
Ans: b. . 0.124 M
7. One way to increase the production of CO gas in the equilibrium at 200 ºC shown below is to
C(coal) + H2O(g) <==> CO(g) + H2(g)
a. decrease the coal supply.
b. decrease the water present.
c. remove H2.
d. decrease the pressure.
Ans: c. remove H2.
8. The homogeneous equilibrium in this list is
a. Ag+(aq) + Cl-(aq) <===> AgCl(s).
b. P 4O10(s)
<===> P4(g) + 5O2(g).
c. HCl(g) + NH3(g) <===> NH4Cl(s). d. HC2H3O2(aq) <===> H+(aq) + C2H3O2-(aq).
Ans: d. HC2H3O2(aq) <===> H+(aq) + C2H3O2-(aq).
9. For the reaction 2 SO2(g) + O2 (g) <===> 2 SO3(g) at 827oC, the value of Kc = 37.1. The Kp for
this reaction at
827oC is (R= 0.08206 atm-L/mol K)
a. 0.412.
b. 6.09.
c. 90.8. d. impossible to calculate from the data available.
Ans: a. 0.412
10. For the gaseous reaction, 2NO(g) + O2(g) <===> 2NO2(g), the constant Kp is equal to:
a. 1.0.
b. Kc(RT)-2.
c. Kc(RT)2.
d. Kc(RT)-1.
e. Kc(RT).
Ans: d Kc(RT)-1.
11. For the reaction
C(s) + CO2(g) <====> 2CO(g) Kc = 168,
determine whether the system is at equilibrium when (CO) = 0.50 M and (CO 2) = 0.75 M. The
system ____ at equilibrium, because ___.
a is; the value of Q is 0.33
.
b is not; the value of Q is
.
0.33
c is; the value of Q is 0.67
.
d is not; the value of Q is
.
0.67
e More information is
.
needed to answer this
question.
ANS: B. is not; the value of Q is 0.33
12. The value of Kc = 1.6 x 10-5 for the reaction
2 NOCl(g) <==> 2 NO(g) + Cl2(g)
at 35°C. If 1.0 mol of each gas were added to a 1.0 L flask, then
a. the pressure in the flask would increase.
b. the concentration of NOCl would increase.
c. mostly product would be present at equilibrium.
d. the value of Kc would become 1.0.
Ans: b. the concentration of NOCl would increase.
13. For the reaction CS2(g) + 3 Cl2(g) <===> S2Cl2(g) + CCl4(g), H° = -84.3 kJ. The change that
would move the
equilibrium position to the left is
a. increasing the temperature. b. adding Cl2 to the system.
c. decreasing the size of the container. d. removing some CCl 4 from the system.
Ans: a. increasing the temperature.
14. A student made a reaction mixture as directed in the lab manual, except he forgot to add the
catalyst. If everyone's experiment reached equilibrium, how was that student's experiment
different?
a The one without a catalyst had less
.
product.
b The one without a catalyst had more
.
product.
c The one without a catalyst took longer
.
to reach equilibrium, but the
amount of product was the same as
in the other experiments.
d The one without a catalyst reached
.
equilibrium faster, but the amount
of product was the same as in the
other experiments.
e The one without a catalyst took longer
.
to reach equilibrium and had much
less product.
ANS: C. The one without a catalyst took longer to reach equilibrium, but the amount of product was the
same as in the other experiments.
15. Which statement concerning product-favored reactions is not correct?
a The value of the equilibrium constant is
.
greater than 1.
b An endothermic reaction is product-favored.
.
c If the entropy of the products is greater than
.
the entropy of the reactants, the reaction is
product-favored.
d If a reaction is product-favored at high
.
temperature, the entropy of the products is
probably greater than the entropy of the
reactants.
e If a reaction is product-favored at low
.
temperature, the enthalpy of the products
is probably less than the enthalpy of the
reactants.
ANS: B. An endothermic reaction is product-favored.