43.(C) Water molecules are neutral. Hydroxide ions (OH–) have a −1 charge. The overall

charge of the complex is +1. Zinc would have to have a +2 charge in order for the com-

plex to end up with a +1 charge. If you let x= the charge of the zinc ion, then

+1 = x+ 3(0) + 1(−1)

x=+2

44.(B) To do this problem, you would use the Clausius-Clapeyron equation:

log. R

H

TT

TT

P

P ∆

2 303

vap

1

2

21

= cm^21 -

where

P 1 (132 mm Hg) is the vapor pressure of the liquid at T 1 (327 K).

P 2 (x) is the vapor pressure of the liquid at T 2 (310 K).

Ris a universal gas constant: 8.314 joules/(mole ⋅K).

Although the problem does not require you to solve the equation, it is presented below.

Substituting the values of the problem into the equation gives

.. /( )

./

log mm Hgx J mole K

J mole

KK

KK

132 2 303 8 314

433 10

310 327

(^4310327)
#:

:

• eo

Simplifying this problem gives you

log 132 x =-0 379.

Solving for xyields x= 55.2 mm Hg.

Note that the question tells you there are 2.00 moles of the compound. This information is

irrelevant to solving the problem since equilibrium vapor pressure is independent of the

amount of compound.

45. (C) This problem can be solved by using the factor-label method.
    100. g solution −10. g solute = 90 g solvent (H 2 0)

.

.

gH O..

gC H O

kg H O

gH O

gC H O

mole C H O m

90

10

1

1000

90

(^112)
2
62
2
2
62
##^62.
46.(B) The Al3+has been diluted tenfold:
.
.
.
cm
Mcm
M
10
10 1
3 010
#^3

47. (D)

.

.

.

.

rate

rate

old conc

new conc

old conc

old conc

1

(^822)
x
x
2 x
1
=== =:
^
^
c
h
h
m
8 = 2x
x = 3
Answers and Explanations for the Practice Test