Q 11-12-126JEE MainJEE Main 2020 (2 Sep, Shift 1)Easy
A gas mixture consists of $3$ moles of oxygen and $5$ moles of argon at temperature $T$. Assuming the gases to be ideal and the oxygen bond to be rigid, the total internal energy (in units of $RT$) of the mixture is:
Answer: (A) $15$
Rigid diatomic oxygen has $5$ degrees of freedom and argon (monatomic) has $3$.
$$U = 3\times\frac52 RT + 5\times\frac32 RT = 7.5RT + 7.5RT = 15RT$$
Solution by Sreeraj P, M.Sc Physics