Question

Assertion :The pressure of a given mass of gas is directly proportional to the absolute temperature at constant volume. Reason: With the increase in temperature, the average kinetic energy of the molecule increases and hence the average velocity of the molecules increases.

• A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
• B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
• C. Assertion is correct but Reason is incorrect
• D. Both Assertion and Reason are incorrect

Answer 1

The correct option is B Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion

By ideal gas equation, $PV=nRT$
If V is constant, then pressure is directly proportional to temperature.

Now, as we increase the temperature, the average kinetic energy of molecules increases (note that average kinetic energy is proportional to kT). So, the average velocity also increases.

But, this reason does not explain the linear relation between pressure and temperature at a constant volume.

Hence, the correct answer is option $\text{B}$.