A gas mixture consists of 2 mol of oxygen and 4 mol of argon at temperature T. Neglecting all vibrational modes, the total internal energy of the system is :

4 RT 15 RT 9 RT 11 RT

11 RT

Total internal energy of system : U U = Uoxygen + Uargon    = \(\mu_1 \frac{f_1}{2}RT + \mu_2 \frac{f_2}{2}RT\)    = \(2*\frac{5}{2}RT + 4*\frac{3}{2}RT\)    = 5 RT + 6 RT = 11 RT