Question

This green solution of chromium(III) can further be reduced by zinc metal to a blue solution of chromium(II) ions. Write the balanced half-reactions and net ionic equation for this reduction.

Answer 1

Half-reactions:

Cr³⁺ + 1e⁻ → Cr²⁺; Zn → Zn²⁺ + 2e⁻

Net ionic equation:

2Cr³⁺ + Zn → 2Cr²⁺ + Zn²⁺

Step-by-step explanation:

The Cr³⁺ is reduced to Cr²⁺:

Cr³⁺ + 1e⁻ → Cr²⁺ -Half-reaction 1-

Zn is oxidized to Zn²⁺:

Zn → Zn²⁺ + 2e⁻ -Half-reaction 2-

Twice the reduction of Cr:

2Cr³⁺ + 2e⁻ → 2Cr²⁺

Now this reaction + Oxidation of Zn:

2Cr³⁺ + 2e⁻ + Zn → 2Cr²⁺ + Zn²⁺ + 2e⁻

2Cr³⁺ + Zn → 2Cr²⁺ + Zn²⁺ - Net ionic equation