NEET2017PhysicsThermodynamicsActual
A gas mixture consists of 2 moles of O 2 and 4 moles of Ar at temperature T . Neglecting all vibrational modes, the total internal energy of the system is ( R is universal gas constant)
Options
- A4 R T
- B15 R T
- C9 R T
- D11 R T
Correct answer
D. 11 R T
Step-by-step solution
For a gas having n moles of molecules with each f degrees of freedom at temperature T K, internal energy is U = 1 2 n f R T ∴ Total internal energy is U = n 1 f 1 2 R T + n 2 f 2 2 R T = 2 × 5 2 R T + 4 × 3 2 R T = 5 R T + 6 R T U = 11 R T