Cliffs AP Chemistry, 3rd Edition

Samples: Multiple-Choice Questions

1. What mass of copper would be produced by the reduction of the Cu2+(aq) ion by passing
   96.487 amperes of current through a solution of copper(II) chloride for 100.00 minutes?
   (1 Faraday = 96,487 coulombs)

A. 95.325 g

B. 190.65 g

C. 285.975 g

D. 381.30 g

E. cannot be determined from the information provided

Answer: B

Step 1: Write the reaction that would occur at the cathode.

Cu2+(aq) +2e–→Cu(s)

Step 2: This problem can be solved by using the factor-label method:

(Note all the conversion factors that you should be comfortable with.)

..

,

.

.

min

min

sec

sec

amperes utes

utes

onds

ampere ond

coulomb

coulombs

Faraday

Faraday

mole e

moles e

mole Cu

mole Cu

gCu

gCu

1

96 487

1

100 0

1

60

1

1

96 487

1

1

1

2

1

1

63 55

190 65

##

# : ##

##=

2. Find E°for a cell composed of silver and gold electrodes in 1 molar solutions of their
   respective ions: E°redAg = +0.7991 volts; E°redAu = +1.68 volts.

A. −0.44 volt

B. 0 volt

C. 0.44 volt

D. 0.88 volt

E. 2.48 volts

Answer: D

Notice that E°redfor silver is lower than E°redfor gold. This means that because silver is higher in
the activity series, silver metal will reduce the gold ion.

Reduction and Oxidation