Q 11-12-146JEE MainJEE Main 2019 (11 Jan, Shift 1)Easy
A gas mixture consists of $3$ moles of oxygen and $5$ moles of argon at temperature $T$. Considering only translational and rotational modes, the total internal energy of the system is
Answer: (A) $15RT$
Oxygen (diatomic): 5 degrees of freedom; argon (monatomic): 3.
$$U = 3\times\frac52RT + 5\times\frac32RT = 7.5RT + 7.5RT = 15RT$$
Solution by Sreeraj P, M.Sc Physics