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What gets reduced in an electrolytic cell made with nickel and copper electrodes?

A. Ni(s)
B.Cu2+
C.Cu(s)
D.Ni2+

User John Moon
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1 Answer

5 votes

Answer:

D. Ni²⁺

Step-by-step explanation:

We know at once that the answer cannot be A or C, because Ni and Cu are already in their lowest oxidation states.

The correct answer must be either B or D.

An electrolytic cell is the opposite of a galvanic cell. In the former, the reaction proceeds spontaneously. In the latter, you must force the reaction to occur.

One strategy to solve this problem is:

  1. Look up the standard reduction potentials for the half reaction·
  2. Figure out the spontaneous direction.
  3. Write the equation in the reverse direction.

1. Standard reduction potentials

E°/V

Cu²⁺ + 2e⁻ ⟶ Cu; 0.3419

Ni²⁺ + 2e⁻ ⟶ Ni; -0.257

2. Galvanic Cell

We reverse the direction of the more negative half cell and add.

E°/V

Ni ⟶ Ni²⁺ + 2e⁻; 0.257

Cu²⁺ + 2e⁻ ⟶ Cu; 0.3419

Ni + Cu²⁺ ⟶ Cu + Ni²⁺; 0.599

This is the spontaneous direction.

Cu²⁺ is reduced to Cu.

3. Electrochemical cell

E°/V

Ni²⁺ + 2e⁻ ⟶ Ni; -0.257

Cu ⟶ Cu²⁺ + 2e⁻; -0.3419

Cu + Ni²⁺ ⟶ Ni + Cu²⁺; -0.599

This is the non-spontaneous direction.

Ni²⁺ is reduced to Ni in the electrolytic cell.

User Cpd
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