Question

Assertion :Molar specific heat at constant volume of an ideal diatomic gas is $\frac{3}{2}R+R$. Reason: On heating 1 mole of an ideal diatomic gas at constant pressure, for $1^{o}C$ rise in temperature, the increase in internal energy of the gas is $\frac{7}{2}R$.

Read the above assertion and reason and choose the correct option regarding it.

• 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. Assertion is incorrect but Reason is correct

Answer 1

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

The average energy of a diatomic molecule is $\frac{5}{2}RT$ at constant $V$
(as the degree of freedom are five)

The average energy of diatomic molecule at constant $P=\frac{7}{2}RT$

$\therefore$ Increase in internal energy $=\frac{7}{2}R(T+1)-\frac{7}{2}RT=\frac{7}{2}R$

So, the correct option is $A$