What is the net redox reaction that occurs when Au comes into contact with acidic KMnO4? (Use the lowest possible coefficients. Omit states-of-matter from your answer.)

3MnO₄⁻ + 24H⁺ + 5Au → 5Au³⁺ + 3Mn²⁺ + 12H₂O.

Explanation:

KMnO₄ is strong oxidizing agent which is reduced and oxidizes Au according to the two-half reactions:

The oxidation reaction: Au → Au³⁺ + 3e.

The reduction reaction: MnO₄⁻ + 8H⁺ + 5e → Mn²⁺ + 4H₂O.

To obtain the net redox reaction, we multiply the oxidation reaction by 5 and the reduction reaction by 5 to equalize the no. of electrons in the two-half reactions.

So, the net redox reaction will be:

3MnO₄⁻ + 24H⁺ + 5Au → 5Au³⁺ + 3Mn²⁺ + 12H₂O.