5 Steps to a 5 AP Chemistry

Equilibrium  233

17.A student wishes to reduce the zinc ion concentra-
tion in a saturated zinc iodate solution to 1 × 10 −^6
M. How many moles of solid KIO 3 must be added
to 1.00 liter of solution? (KspZn(IO 3 ) 2 = 4 × 10 −^6
at 25°C)
(A) 1 mol
(B) 0.5 mol
(C) 0.0001 mol
(D) 4 mol
(E) 2 mol

18.At constant temperature, a change in volume will
NOT affect the moles of substances present in
which of the following?
(A) H 2 (g) +I 2 (g) 2HI(g)
(B) CO(g) + Cl 2 (g) COCl 2 (g)
(C) PCl 5 (g) PCl 3 (g) +Cl 2 (g)
(D) N 2 (g) + 3 H 2 (g) 2 NH 3 (g)

(E) CH 4 (g) + CO 2 (g) 2 CO(g) + 2 H 2 (g)

19.The equilibrium constant for the hydrolysis of
C 2 O 42 − is best represented by which of the
following?
(A)K=[OH−][C 2 O 42 −]/[HC 2 O 4 −]
(B)K=[H 3 O+][C 2 O 42 −]/[HC 2 O 4 −]
(C)K=[HC 2 O 4 −][OH−]/[C 2 O 42 −]
(D)K=[C 2 O 42 −]/[HC 2 O 4 −][OH−]
(E)K=[C 2 O^24 −]/[HC 2 O 4 −][H3O+]

20.IO 3 −+HC 2 H 3 O 2 HIO 3 +C 2 H 3 O 2 −

The above equation has an equilibrium constant

that is less than 1. What are the relative strengths

of the acids and bases?

ACIDS BASES

A. HIO 3 < HC 2 H 3 O 2 IO 3 −< C 2 H 3 O 2 −

B. HIO 3 < HC 2 H 3 O 2 IO 3 −> C 2 H 3 O 2 −

C. HIO 3 > HC 2 H 3 O 2 IO 3 −> C 2 H 3 O 2 −

D. HIO 3 > HC 2 H 3 O 2 IO 3 −< C 2 H 3 O 2 −

E. HIO 3 =HC 2 H 3 O 2 IO 3 −=C 2 H 3 O 2 −

21.ZnS(s) +2H+(aq) Zn^2 +(aq) +H 2 S(aq)

What is the equilibrium constant for the above

reaction? The successive acid dissociation con-

stants for H 2 S are 9.5 × 10 −^8 (Ka1) and 1 × 10 −^19

(Ka2). Ksp, the solubility product constant, for

ZnS equals 1.6 × 10 −^24.

(A) 1.6 × 10 −^24 /9.5 × 10 −^8

(B) 1 × 10 −^79 /1.6 × 10 −^24

(C) 9.5 × 10 −^27 /1.6 × 10 −^24

(D) 9.5 × 10 −^8 /1.6 × 10 −^24

(E) 1.6 × 10 −^24 /9.5 × 10 −^27

22.H 2 PO 4 −+H 2 O H 3 O++HPO 42 −

Which species, in the above equilibrium, behave

as bases?

I. HPO 42 −

II. H 2 PO 4 −

III. H 2 O

(A) I only

(B) I and II

(C) II and III

(D) I and III

(E) III only

23.H 2 C 3 H 2 O 4 +2 H 2 O 2 H 3 O++C 3 H 2 O 42 −

As shown above, malonic acid is a diprotic acid.

The successive equilibrium constants are 1.5 ×

10

− 3

(Ka1) and 2.0 × 10

− 6

(Ka2). What is the equi-

librium constant for the above reaction?

(A) 1.0 × 10 −^14

(B) 2.0 × 10 −^6

(C) 4.0 × 10 −^12

(D) 3.0 × 10 −^9

(E) 1.5 × 10 −^3

24.C(s) +H 2 O(g) CO(g) +H 2 O(g) endothermic

An equilibrium mixture of the reactants is placed

in a sealed container at 150°C. The amount of

the products may be increased by which of the

following changes?

I. raising the temperature of the container

II. increasing the volume of the container

III. adding 1 mol of C(s) to the container

(A) II only

(B) I and II

(C) I only

(D) II and III

(E) III only