Question

Describe the oxidising action of K₂Cr₂O₇, and write the ionic equations for its reaction with

1. H₂S
2. SO₂

Answer 1

In K₂Cr₂O₇, oxidation number of Cr is +6 but its +3 state is more stable, as a result K₂Cr₂O₇ acts as a good oxidising agent, particularly in acidic medium.

1. Cr₂O^2-₇ + 3S^2- + 14H⁺ → 2Cr³⁺ + 3S + 7H₂O
2. Cr₂O^2-₇ + 3SO₂ + 2H⁺ → 2Cr³⁺ + 3SO^2-₄ + H₂O