A table of standard reduction potentials gives E ?red values for common half-rea

Question

A table of standard reduction potentials gives E?red values for common half-reactions.

Reduction half-reaction

E? (V)

Ag+(aq)+e??Ag(s)

0.80

Cu2+(aq)+2e??Cu(s)

0.34

Ni2+(aq)+2e??Ni(s)

?0.26

Fe2+(aq)+2e??Fe(s)

?0.45

Zn2+(aq)+2e??Zn(s)

?0.76

Part A

Calculate the standard potential for the following galvanic cell:

Zn(s) | Zn2+(aq) || Cu2+(aq) | Cu(s)

Express your answer to three significant figures and include the appropriate units.

Part B

In the context of the zinc-copper cell described in Part A, tell whether each of the following descriptions is anode or cathode.

Zn

Cu

Gains mass

Loses mass

Attracts electrons

Positive electrons

Negative electrode

Stronger reducing agent

Reduction half-reaction

E? (V)

Ag+(aq)+e??Ag(s)

0.80

Cu2+(aq)+2e??Cu(s)

0.34

Ni2+(aq)+2e??Ni(s)

?0.26

Fe2+(aq)+2e??Fe(s)

?0.45

Zn2+(aq)+2e??Zn(s)

?0.76

Explanation / Answer

oxidation:

Zn(s)  Zn2+(aq) + 2 e-

Eoox. = - Eored. = - (- 0.76 V) = + 0.76 V

reduction:

Cu2+(aq) + 2 e- Cu(s)

Eored. = + 0.34 V

overall:

Zn(s) + Cu2+(aq)  Zn2+(aq) + Cu(s)

Eocell = + 1.10 V

oxidation:

Zn(s)  Zn2+(aq) + 2 e-

Eoox. = - Eored. = - (- 0.76 V) = + 0.76 V

reduction:

Cu2+(aq) + 2 e- Cu(s)

Eored. = + 0.34 V

overall:

Zn(s) + Cu2+(aq)  Zn2+(aq) + Cu(s)

Eocell = + 1.10 V

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