Cliffs AP Chemistry, 3rd Edition

Step 1: Write the net cell reaction.

Ag(s) + Au+(aq) EAg+(aq) + Au(s)

Step 2: Write the two half-reactions and include the E°redand E°oxvalues.

:

:

ox Ag Ag e

red Au e Au

Ag Au Ag Au

saq

aq s

saq aqs

E

E

E

+

++

+-+

+-

++

^ _

_ ^

^ __^

h i

i h

h iih

.

.

.

E volt

E volts

E volt

0 7991

168

088

ox

red

=-

=

=+

%

%

%

Because the sign of E°is positive, the reaction will proceed spontaneously.

3.... FeCl 2 +... KMnO 4 +... HCl →... FeCl 3 +... KCl +... MnCl 2 +? H 2 O

When the equation for this reaction is balanced with the lowest whole-number

coefficients, the coefficient for H 2 O is

A. 1

B. 2

C. 3

D. 4

E. 5

Answer:D

Step 1:Decide what elements are undergoing oxidation and what elements are undergoing
reduction.

ox: Fe2+"Fe3+

red: MnO 4 - "Mn^2 +

Step 2: Balance each half-reaction with respect to atoms and then charges.

ox: Fe2+"Fe3++ e–

Balance the reduction half-reaction, using water to balance the O’s.

red: MnO 4 - "Mn^2 ++ 4 HO 2

Balance the H atoms with H+ions.

red: MnO 4 - + 8 H+"Mn^2 ++ 4 HO 2

Part II: Specific Topics