Q154 · CSIR NET Chemistry, June 2011
Paper: CSIR NET June 2011 · Subject: Physical Chemistry · Chapter: Atomic and Molecular Term Symbol · Topic: Atomic And Molecular Term Symbols – General · Marks: 2 · Difficulty: Medium
An ideal gas expands by following an equation $\mathrm{PV}^{a}=$ constant. In which case does one expect heating?
(a)$3>$ a $>2$
(b)$2>\mathrm{a}>1$
(c)$0<$ a $<1$
(d)$-1<$ a $<0$
Answer
Answer: C ✓ checked by 4AB · confidence medium
The source book printed B; on checking, C is correct — see the explanation.
Printed B; for a > 1 an expanding gas cools.
Explanation
For PVᵃ = constant, T ∝ V^(1−a); the gas warms on expansion when a < 1. Among the options with a positive exponent that is 0 < a < 1 (a = 1 isothermal, a = γ adiabatic cooling).
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