Question

A student takes a mixture of sand and ammonium chloride in a china dish and heats it under a funnel fitted with a plug over a flame. He would observe that :
(1) solid sand gets deposited on the lower cooler parts of the funnel while solid ammonium chloride remains in the china dish.
(2) sand and ammonium chloride get deposited on hotter parts of the funnel.
(3) ammonium chloride gets deposited on the cooler parts of the funnel and sand remains in the china dish.
(4) sand collects on cooler parts of the funnel while ammonium chloride melts in the china dish.

Answer 1

Solid ammonium chloride directly converts to gas phase on heating, and these vapours are then collected at the cooler parts of the funnel, while sand remains on the china dish. This conversion of solid directly into the gaseous phase in known as sublimation.

Hence, the correct answer is option 3.