Question

A gas mixture consists of 2 mole of oxygen and 4 mole of 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

Answer 1

Answer: (D)

11 RT

Answer 2

Total internal energy of system

$= U_{\text{oxygen}} + U_{\text{argon}} = \mu_{1}\frac{f_{1}}{2}RT + \mu_{2}\frac{f_{2}}{2}RT$

$= 2\frac{5}{2}RT + 4\frac{3}{2}RT = 5RT + 6RT = 11RT$

[As f₁ = 5 (for oxygen) and f₂ = 3 (for argon)]