Question

Assertion: The ratio $C_p/C_v$ is more for helium gas than for hydrogen gas.
Reason: All metals acts as black bodies.

• A. If both Assertion and Reason are true and the Reason is a correct explanation of the Assertion
• B. If both Assertion and Reason are true but Reason is not a correct explanation of the Assertion
• C. If Assertion is true but the Reason is false
• D. If both Assertion and Reason are false

Answer 1

Answer: (D)

We know that $\gamma=\frac{C_{p}}{C_{v}}$ for a gas is given by $\gamma=1+\frac{2}{n}$
where $n$ is the degrees of freedom.
Now fora monatomic gas like hydrogen, $n =3$
$\therefore \gamma=1+\frac{2}{3}=1.67$
And for a diatomic gas, $n =5$
$\therefore \gamma=1+\frac{2}{5}=1.4$
$\therefore \gamma _{H e}<\gamma H$