Question

Given below are two statements :
Statement I: Sublimation is used for the separation and purification of compounds with low melting point.
Statement II: The boiling point of a liquid increases as the external pressure is reduced.
In the light of the above statements, choose the correct answer from the options given below :

• A. Both Statement I and Statement II are false
• B. Statement I is false but Statement II is true
• C. Statement I is true but Statement II is false
• D. Both Statement I and Statement II are true

Hint:

Boiling occurs when Vapor Pressure = External Pressure. If you lower the external pressure, the liquid needs less heat to reach that pressure, hence a lower boiling point.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Sublimation is a phase transition from solid to gas without passing through the liquid phase. Boiling point behavior is governed by the relationship between vapor pressure and external pressure.

Step 2: Detailed Explanation:
Statement I is false: Sublimation is used for substances that have high vapor pressures at temperatures below their melting points (sublimable solids like iodine or camphor). It is not defined by "low melting point" alone, but by the ability to bypass the liquid phase.
Statement II is false: The boiling point of a liquid decreases as external pressure is reduced. This is why water boils at a lower temperature on mountains where atmospheric pressure is low.
Step 3: Final Answer:
Both Statement I and Statement II are false.