alleryFor diatomic gas at very high T (vibrational modes active), DOF = ?
A3
B7 (3 trans + 2 rot + 2 vib; γ = 9/7)
C5
D9
Answer & Solution
Correct answer: B. 7 (3 trans + 2 rot + 2 vib; γ = 9/7)
At very high T (above vib quantum gap), 2 more vibrational DOF unlock (kinetic + potential).
Total f = 7, γ = 1 + 2/7 = 9/7. Hence diatomic γ drops with T (5/3 → 7/5 → 9/7 if vib excited).
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