Question

Assertion $\left(A\right)$ : Gases do not liquefy above their critical temperature, even on applying high pressure.

Reason $\left(R\right)$ : Above critical temperature, the molecular speed is high and intermolecular attractions cannot hold the molecules together because they escape because of high speed.

• A. $A$ is true but $R$ is false.
• B. Both $A$ and $R$ are true, and $R$ is the correct explanation of $A$.
• C. $A$ is false but $R$ is true.
• D. Both $A$ and $R$ are true, but $R$ is not the correct explanation of $A$.

Answer 1

The correct option is B Both $A$ and $R$ are true, and $R$ is the correct explanation of $A$.

Analysing the assertion & reason

Gases do not liquefy above their critical temperatures, even on applying high pressure because as the temperature reaches above the critical temperature, the speed of the molecules become very high due to which the intermolecular attractions are not enough to hold the molecules together.
Hence, they escape because of their high speed.
Therefore, both assertion and reason are correct, and reason is the correct explanation of assertion.