Q 11-12-052JEE MainJEE Main 2024 (29 Jan, Shift 2)Medium
$N$ moles of a polyatomic gas ($f = 6$) must be mixed with two moles of a monoatomic gas so that the mixture behaves as a diatomic gas. The value of $N$ is:
Answer: (C) 4
$C_v$ of the mixture must equal $\frac52R$:
$$\frac{N(3R) + 2\left(\frac32R\right)}{N + 2} = \frac52R$$
$$3N + 3 = \frac52N + 5 \;\Rightarrow\; \frac N2 = 2 \;\Rightarrow\; N = 4$$
Solution by Sreeraj P, M.Sc Physics