Question

20. Which substance among those mentioned below sublimes in open air?
a) Sugar
b) Paraffin
c) Sodium chloride
d) Solid carbon dioxide​

Answer 1

Solid Carbon di-oxide sublimes in open air.

Explanation:

• Sublimation: Sublimation is a process in which a substance transforms directly into gaseous form from its solid state, without undergoing the liquid state.
• Solid Carbon di-oxide, also known as Dry ice, sublimes when kept in open air.
• Solid Carbon di-oxide is the frozen Carbon di-oxide. It goes under the process of sublimation at a low temperature of -78 degrees celcius under normal pressure of atmosphere i.e. 1 atm.

Answer 2

Answer:

Correct option is

C

Sodium chloride

Explanation:

Sodium Chloride is an ionic solid and has high melting and boiling points. So it can not change in vapour phase simply at atmospheric pressure hence it cannot sublime.

Ammonium chloride, dry ice and iodine undergo sublimation which on heating without coming in the liquid state directly convert in a gaseous state.

Hence, the correct answer is option C.