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 :

1. 15 RT

2. 9 RT

3. 11 RT

4. 4 RT

Doubtly Asked 30 Oct 2026 NEET UG 2017 Practice test neet Save WhatsApp Report

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Answer: 3. 11 RT

Key idea: internal energy \(U=\dfrac f2nRT\).

\(\mathrm{O_2}\) is diatomic (\(f=5\), vibration neglected): \(U=\tfrac52\times2RT=5RT\).

Ar is monatomic (\(f=3\)): \(U=\tfrac32\times4RT=6RT\).

Total \(=11RT\).

Doubtly AI · 30 Oct 2026 AI-generated · not yet verified Report

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