1(vi)
What do you observe when concentrated hydrochloric acid is added to manganese dioxide and then heated?
- (a)A colourless gas is liberated that puts out a burning splinter with a 'pop' sound.
- (b)A reddish-brown gas is liberated that turns moist potassium iodide paper brown.
- (c)A colourless gas is liberated that turns lime water milky.
- (d)A greenish yellow gas is liberated that turns moist starch iodide paper blue-black.
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A greenish yellow gas is liberated that turns moist starch iodide paper blue-black.
Reason — Manganese dioxide oxidises concentrated hydrochloric acid on heating to liberate chlorine, a greenish-yellow gas. Chlorine liberates iodine from starch iodide paper, turning it blue-black.
MnO2 + 4HCl ⟶ MnCl2 + 2H2O + Cl2