Question

When SO₂ gas is passed through the acidified K₂Cr₂O₇ solution, the colour of the solution changes to ______.

Options

• Red

• Black

• Orange

• Green

Answer 1

When SO₂ gas is passed through the acidified K₂Cr₂O₇ solution, the colour of the solution changes to green.

Explanation:

Acidified potassium dichromate (K₂Cr₂O₇, orange) is an oxidising agent.
When SO₂ is passed through it, SO₂ acts as a reducing agent and reduces Cr⁶⁺ (orange) to Cr³⁺ (green). Therefore, the solution turns green.