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-Reaction                            E° (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.

Answer 1

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⁺