A strip of chromium is placed in a 1 M solution of chromium (III) sulfate, and a

Question

A strip of chromium is placed in a 1 M solution of chromium (III) sulfate, and a strip of copper is placed in a 1 M solution of copper(II) chloride. The two solutions are connected with a salt bridge, and the two metals are connected by a wire. bridge, and the two metals are connected by a wire.

Reduction Half-ReactionE° (V)

Cr3+(aq)+3e–Cr(s)–0.74

Cu2+(aq)+2e– Cu(s)0.34

Which of the following takes place?

a. Sulfur deposits at the iron electrode.

b. The Cr(III) concentration of the iron half-cell decreases.

c. Copper atoms deposit at the cathode.

d. Chlorine is produced at the copper electrode.

e. Chlorine is produced at the chromium electrode.

Explanation / Answer

Answer 'C'

The standard reduction potentials are

Cr3+(aq)+3e–Cr(s)E0=–0.74V

Cu2+(aq)+2e– Cu(s)E0 =0.34V

Copper acts as cathode as it has positive E0

Reduction takes place at cathode (Copper deposited at cathode)

Cu2+(aq)+2e– Cu(s)     -------------(1)

Oxidation takes place at anode

Cr(s) Cr3+(aq)+3e–          ------------ (2)

The net balanced cell reaction (1) x 3 + (2)x 2 ===>

3 Cu2+ + 2 Cr 3 Cu + 2 Cr3+

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