1(xiii)
When compound X reacts with dilute hydrochloric acid, it releases a gas that turns moist lead acetate paper black and decolourises acidified potassium permanganate solution. Which of the following is compound X?
- (a)Sodium nitrate
- (b)Sodium sulphide
- (c)Sodium carbonate
- (d)Sodium sulphite
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Sodium sulphide
Reason — Sodium sulphide reacts with dilute hydrochloric acid to release hydrogen sulphide gas. H2S turns moist lead acetate paper black (due to the formation of black lead sulphide) and being a reducing gas, it also decolourises acidified potassium permanganate solution.
Na2S + 2HCl ⟶ 2NaCl + H2S ↑