746 CHAPTER 17: Chemical Equilibrium
0 27.For the reactionCO(g)H 2 O(g) 34 CO 2 (g)H 2 (g)the value of the equilibrium constant, Kc, is 1.845 at a given
temperature. We place 0.500 mole CO and 0.500 mole
H 2 O in a 1.00-L container at this temperature, and allow
the reaction to reach equilibrium. What will be the equi-
librium concentrations of all substances present?
0 28.Given: A(g)B(g) 34 C(g)2D(g)
One mole of A and one mole of B are placed in a 0.400-liter
container. After equilibrium has been established,
0.20 mole of C is present in the container. Calculate the
equilibrium constant, Kc, for the reaction.
0 29.Nitrogen reacts with hydrogen to form ammonia.N 2 (g)3H 2 (g) 34 2NH 3 (g)An equilibrium mixture at a given temperature is found to
contain 0.31 mol/L N 2 , 0.50 mol/L H 2 , and 0.14 mol/L
NH 3. Calculate the value of Kcat the given temperature.
0 30.For the following equation, Kc7.9 1011 at 500 K.H 2 (g)Br 2 (g) 34 2HBr(g)(a) 2 ^1 H 2 (g)^12 Br 2 (g) 34 HBr(g) Kc?
(b) 2HBr(g) 34 H 2 (g)Br 2 (g) Kc?
(c) 4HBr(g) 34 2H 2 (g)2Br 2 (g) Kc?
0 31.The equilibrium constant for the reaction2SO 2 O 234 2SO 3is Kc279 at a given high temperature. What is the value
of the equilibrium constant for each of the following
reactions at this temperature?
(a) 2SO 334 2SO 2 O 2
(b) SO 2 ^12 O 234 SO 3
0 32.A sealed tube initially contains 9.84 10 ^4 mol H 2 and
1.38 10 ^3 mol I 2. It is kept at 350°C until the reactionH 2 (g)I 2 (g) 34 2HI(g)comes to equilibrium. At equilibrium, 4.73 10 ^4 mol I 2
is present. Calculate (a) the numbers of moles of H 2 and
HI present at equilibrium; (b) the equilibrium constant,
Kc, for the reaction.
0 33.NO and O 2 are mixed in a container of fixed volume kept
at 1000 K. Their initial concentrations are 0.0200 mol/L
and 0.0300 mol/L, respectively. When the reaction2NO(g)O 2 (g) 34 2NO 2 (g)has come to equilibrium, the concentration of NO 2 is
2.2 10 ^3 mol/L. Calculate (a) the concentration of NO
at equilibrium, (b) the concentration of O 2 at equilibrium,
and (c) the equilibrium constant, Kc, for the reaction.0 34.Antimony pentachloride decomposes in a gas-phase reac-
tion at high temperatures.SbCl 5 (g) 34 SbCl 3 (g)Cl 2 (g)(a) At some temperature, an equilibrium mixture in a
5.00-L container is found to contain 6.91 g of SbCl 5 ,
16.45 g of SbCl 3 , and 5.11 g of Cl 2. Evaluate Kc.
(b) If 10.0 grams of SbCl 5 is placed in the 5.00-liter
container and allowed to establish equilibrium at the
temperature in part (a), what will be the equilibrium
concentrations of all species?
0 35.At standard temperature and pressure, the reaction indi-
cated by the following equation has an equilibrium con-
stant, Kc, equal to 0.0212HI(g) 34 H 2 (g)I 2 (g)Calculate the equilibrium constant, Kc, for the reverse
equation.
0 36.The following reaction has an equilibrium constant, Kc,
equal to 1538 at 1800°C2NO(g)O 2 (g) 34 2NO 2 (g)Calculate the equilibrium constant, Kc, for the reverse
equation.The Reaction Quotient, Q
0 37.Define the reaction quotient, Q.Distinguish between Q
and K.
0 38.Why is it useful to compare Qwith K?What is the situa-
tion when (a) QK? (b) Q K? (c) Q K?
0 39.How does the form of the reaction quotient compare with
that of the equilibrium constant? What is the difference
between these two expressions?
0 40.If the reaction quotient is larger than the equilibrium con-
stant, what will happen to the reaction? What will happen
if Q K?
0 41.Kc19.9 for the reactionCl 2 (g)F 2 (g) 34 2ClF(g)What will happen in a reaction mixture originally
containing [Cl 2 ]0.4 mol/L, [F 2 ]0.2 mol/L, and
[ClF]7.3 mol/L?
42.The concentration equilibrium constant for the gas-phase
reactionH 2 CO 34 H 2 COhas the numerical value 0.50 at a given temperature. A
mixture of H 2 CO, H 2 , and CO is introduced into a flask
at this temperature. After a short time, analysis of a small
sample of the reaction mixture shows the concentrations
to be [H 2 CO]0.50 M,[H 2 ]1.50 M,and [CO]