Question

Conversion of vapour into solid on cooling is called
A. desublimation
B. Vapour deposition
C. both A and B
D. None of the above

Answer 1

Hint: The process of conversion of the vapour into solid by the cooling is an endothermic process because heat or energy is absorbed by the molecules. The process is the reverse of sublimation and takes place below the triple point.

Complete Step-by-Step Answer:
- In the given question, we have to name the process when the vapour converts into the solid-state on cooling.
- As we know that sublimation is the process in which the conversion of solid into the vapour phase takes place.
- For example, the conversion of dry ice or frozen carbon dioxide directly into the gaseous form.
- The compound which undergoes sublimation process has the characteristic property of triple point i.e. the point at which the substance can exist in all the three states.
- Whereas when the process of sublimation is reversed that is the vapour directly converts into the solid then it is known as de-sublimation. Here, the 'de' means the reverse.
- Whereas vapour deposition means the deposition or aggregation of the vapours by cooling to form a solid.
- The most common example of desublimation is the conversion of water vapour into ice when placed in the cold air.
- So, we can say that both options A and B describe the conversion of vapour into solid correctly.

Therefore, option C is the correct answer because both the statements are correct.

Note: The conversion of the solid-state into liquid state is known as melting and the temperature at which the substance melts is known as the melting point. Whereas conversion of liquid to the solid-state is known as the freezing or solidification.