Q 11-12-028JEE MainJEE Main 2026 (6 Apr, Shift 2)Easy
If $2$ mole of an ideal monoatomic gas at temperature $T$, is mixed with $6$ mole of another ideal monoatomic gas at temperature $2T$ then the temperature of mixture is:
Answer: (D) $\dfrac{7}{4}T$
Concept. When gases mix in isolation, the total internal energy is conserved. For monatomic gases $U=\tfrac32nRT$, so $\sum n_iT_i=(\sum n_i)T$.
Step 1. Energy balance. $2T+6(2T)=8T_f$.
Step 2. Solve. $T_f=\dfrac{14T}{8}=\dfrac74T$.
Answer. Option D.
Solution by Sreeraj P, M.Sc Physics
