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NEET 2017 · Degrees of Freedom & Internal Energy

Degrees of Freedom & Internal Energy question from NEET 2017

Q35NEET 2017Medium

Degrees of Freedom & Internal Energy

A gas mixture consists of 2 moles of O2 and 4 moles of Ar at temperature T. Neglecting all vibrational modes, the total internal energy of the system is

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Answer: (c)

  1. U=∑nf2RTU = \sum n\frac{f}{2}RT; O2\text{O}_2 (no vibration) f=5f = 5, Ar f=3f = 3.
  2. U=2×52RT+4×32RT=5RT+6RTU = 2 \times \frac{5}{2}RT + 4 \times \frac{3}{2}RT = 5RT + 6RT
  3. So the answer is (c) 11RT11RT.
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