State one appropriate observation for : conc. H₂SO₄ is added to a crystal of hydrated copper sulphate.

In the given equation :

S + 2H₂SO₄ ⟶ 3SO₂ + 2H₂O

Identify the role played by conc. H₂SO₄ i.e.

(A) Non-volatile acid

(B) Oxidising agent

(C) Dehydrating agent

(D) None of the above.

Identify the substance underlined: A dilute mineral acid which forms a white precipitate when treated with barium chloride solution.

Write balanced equations for the following: Action of concentrated sulphuric acid on carbon.