Q. A gas mixture consists of 2 moles of oxygen and 4 moles argon at temperature $T$. Neglecting all vibrational modes, the total internal energy of the system is
A) $4\ RT$
B) $15\ RT$
C) $9\ RT$
D) $11\ RT$
Explanation
(d) Oxygen is diatomic gas, hence its energy of two moles
$= 2 \times \frac{5}{2}RT = 5RT$
Argon is a monoatomic gas, hence its internal energy of 4 moles $= 4 \times \frac{3}{2}RT = 6RT$
Total Internal energy $= (6 + 5)RT = 11RT$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.