Question

On heating, some solid substances change from solid to vapour state without passing through liquid state. The technique used for the purification of such solid substances based on the above principle is known as

• A. Crystallization
• B. Sublimation
• C. Distillation
• D. Chromatography

Answer 1

The Correct Option is B

Step 1: Define Sublimation

Sublimation is the process in which a solid directly converts into vapor without becoming a liquid. 

Step 2: Examples of Sublimation

• Common sublimely substances: Camphor, iodine, naphthalene.
• Purification process: Impure substances are heated, and the pure substance sublimes, leaving impurities behind.

Step 3: Compare with Other Techniques

• Distillation: Used for liquid purification.
• Chromatography: Separates mixtures based on differential absorption.
• Crystallization: Used for solids but involves solubility differences.

Step 4: Conclusion

Sublimation is the correct purification method in this context because it allows the separation of a substance that directly sublimates, leaving impurities behind.