Total Internal Energy of a Gas Mixture – Rankers Physics

Kinetic Theory of Gases: Practice Problem & Solution

A gas mixture consists of 5 moles of oxygen and 3 moles of argon at temperature T. Assuming the gases to be ideal and oxygen bond to be rigid, the total internal energy of the mixture is (where R denotes the universal gas constant)
17RT
15RT
20RT
11RT

Solution Explained:

To solve this problem, we apply the core principles of Kinetic Theory of Gases. Understanding the underlying formula is key to arriving at the correct answer below:

Internal energy is \( U = n \frac{f}{2} RT \). For diatomic \( \text{O}_2 \) (rigid, \( f_1=5 \)), \( U_1 = 5 \times \frac{5}{2} RT = 12.5 RT \). For monoatomic \( \text{Ar} \) (\( f_2=3 \)), \( U_2 = 3 \times \frac{3}{2} RT = 4.5 RT \). Total \( U = 12.5RT + 4.5RT = 17RT \).

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