QQuestion
State a relevant reason for the following: [2]
(a) Hydrogen chloride gas cannot be dried over quick lime.
(b) Ammonia gas is not collected over water.
✓Answer
(a) Quicklime (CaO) reacts with hydrogen chloride, forming calcium chloride and water. It would absorb the gas itself, so it cannot be used to dry HCl.
CaO + 2HCl → CaCl2 + H2O
(b) Ammonia is highly soluble in water and would dissolve instead of being collected.
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