Question

Identify the anion present in the following compound.

Compound Z which on reacting with dilute sulphuric acid liberates a gas that has no effect on acidified potassium dichromate but turns lime water milky.

Answer 1

Carbonate ion \[\ce{(CO^{2-}3)}\]

Explanation:

Compound Z is a salt of carbonate \[\ce{(CO^{2-}3)}\] or bicarbonate \[\ce{HCO^-3}\]. Carbonates and bicarbonates react with dilute sulphuric acid to give metallic sulphate, water, and carbon dioxide gas. This gas has no effect on acidified potassium dichromate, but it turns lime water milky, which confirms the evolution of carbon dioxide gas during the reaction.