Question

Name the anion [negative ion] present in the following compound:

Compound D when warmed with dilute H₂SO₄ gives a gas which turns acidified potassium dichromate solution green.

Answer 1

Sulphuric acid, when treated with sulphites gives sulphate salts, water and sulphur dioxide gas. Sulphur dioxide turns potassium dichromate solution green. Thus, the negative ion is Sulphite ion. 

Answer 2

Compound D is Na₂SO₃ and anion is \[\ce{[SO^{2-}3]}\].