Cliffs AP Chemistry, 3rd Edition

(c) Restatement: What happens at the anode?

Oxidation occurs at the anode. Silver is lower in the activity series than copper. Therefore,

the oxidation half-reaction is

ox: Cu(s) →Cu2+(aq)+ 2 e–

(d) Restatement: Overall cell equation.

Combining these two half-equations into one cell equation produces

:.+

:.

.

ox Cu s Cu aq e

red Ag aq e Ag s

Cu s Ag aq Cu aq Ag s

E

E

E

2 0 337

2 2 2 0 7991

2 2 0 462

cell

red

cell

2

2

"

"

"

+=-

+=+

++=

+-

++

%

%

%

^ _

_ ^

^ __^

h i

i h

h iih

The overall theoretical E°cellis 0.7991 −0.337 = +0.462 volt. Because this reaction is spon-

taneous, as was discovered when the cell was measured, producing the experimentally de-

termined 0.42 volt, this is in agreement with our cell designations.

(e) Restatement: Cell notation.

Cu(s) | Cu2+(aq) || Ag+(aq) | Ag(s)

(f) Given:

4 M NH 3 (aq)added to CuSO 4 solution →Cu(NH 3 ) 4 2+(aq)

Voltage = 0.88 volt

Restatement: Calculate [Cu2+(aq)].

Because this cell is not operating under standard conditions, you will need to use the

Nernst equation:

EE. log

n Qat C

0 0592 25

cell=-cell% %

The variables take on the following values:

Ecell= 0.88 volt

E°cell= 0.46 volt

Q

aq

aq x

x

Ag

Cu

(^221)
2
===+

• 
  
  i
  i
  9
  9
  C
  C
  Substituting into the Nernst equation yields
  088 046..=-0 0592. 2 logx
  0.0296 log x= −0.42
  .
  logx.
  0 0296
  ==-^04214
  So [Cu2+(aq)] = 1.0 x 10–14M
  Part II: Specific Topics