Study the following observations and name the anions present in each of the reactions.

Study the following observations and name the anions present in each of the reactions.

(a) When a crystalline solid 'P' is warmed with concentrated H₂SO₄ and copper turnings a reddish brown gas is released.

(b) When few drops of dilute sulphuric acid is added to Salt 'R' and heated, a colourless gas is released which turns moist lead acetate paper silvery black.

(c) When few drops of barium nitrate solution is added to the salt solution 'Q', a white precipitate is formed which is insoluble in HCl.