Question

A gas mixture consist 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_oxygen + U_argon = µ₁ $\frac{f_{1}}{2}$RT + µ₂$\frac{f_{2}}{2}$RT

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

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