Question

In a particular redox reaction, Cr is oxidized to CrO2−4 and Cu2+ is reduced to Cu+. Complete and balance the equation for this reaction in acidic solution. Phases are optional.

Answer 1

The balanced equation for the redox reaction is:

Cr + Cu^2+ + H^+ → CrO_4^2- + Cu^+

To balance this equation, we follow these steps:

1. Write the unbalanced equation with the correct formulas for each compound:

Cr + Cu^2+ → CrO_4^2- + Cu+

1. Break the reaction into two half-reactions, one for the oxidation and one for the reduction:

Oxidation: Cr → CrO_4^2- Reduction: Cu^2+ → Cu+

1. Balance each half-reaction separately:

Oxidation: Cr → CrO_4^2- + 4H+ + 3e- Reduction: Cu^2+ + 2e- → Cu+

1. Balance the electrons by multiplying the oxidation half-reaction by 2 and the reduction half-reaction by 3:

Oxidation: 2Cr → 2CrO_4^2- + 8H+ + 6e- Reduction: 3Cu^2+ + 6e- → 3Cu+

1. Add the half-reactions together, canceling out the electrons:

2Cr + 3Cu^2+ + 8H+ → 2CrO_4^2- + 3Cu+

Therefore, the balanced equation for the redox reaction in acidic solution is:

2Cr + 3Cu^2+ + 8H+ → 2CrO_4^2- + 3Cu+ + 4H2O