Name: Process of Sublimation
Uploaded: 2019-07-19
Duration: 3 min 57 s
Description: Sublimation is converting a substance directly from the solid to the gaseous state of matter without passing through the liquid state. Watch this video.

Question

Describe the process of sublimation by taking the example of ammonium chloride.

Accepted Answer

The change of state directly from solid to gas (or vapours) on heating and vice-versa on cooling, without passing through liquid state is called sublimation.

It should be noted that

(a) The change of a solid directly into gas (or vapour) is known as sublimation, and

(b) The change of gas (or vapour) directly into solid is also known as depostion.

The solid substance that undergoes the process of sublimation is called sublime, while the solid which is obtained by cooling of the vapours of the solid is called sublimate.

The Experiment of ammonium chloride is as follows:

Take some ammonium chloride. Crush it and put it in a clean and dry china dish. Cover the china dish with a filter paper. Put an inverted funnel over the filter paper as shown in Fig. Put a cotton plug on the stem of the funnel to prevent the ammonium chloride vapours from escaping into the atmosphere, as shown in Fig.

Place the apparatus on tripod stand and heat it slowly using a Bunsen burner. It is observed that on heating the china dish, the vapours of ammonium chloride rise up, through the holes of the filter Tripod stand paper and get cooled in the upper portion of the funnel on coming in contact with the cold, inner walls of the funnel and thus, change into the solid form (sublimate). The solid, thus, formed gets deposited on the inner walls of the funnel. When the experiment is completed, the pure solid is scrapped from the inverted funnel with a spatula or a knife on a clean watch glass.

Describe the process of sublimation by taking the example of ammonium chloride.

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