4AB › Chemistry PYQ › CSIR-NET › December 2019 › Q109Q109 · CSIR-NET Chemistry, December 2019 Paper: CSIR-NET December 2019 · Subject: Physical Chemistry · Chapter: Atomic and Molecular Term Symbol · Topic: Atomic And Molecular Term Symbols – General · Marks: 2 · Difficulty: Medium
A monoatomic perfect gas undergoes expansion from $\left(\mathrm{p}_{1}, \mathrm{V}_{1}\right)$ to $\left(\mathrm{p}_{2}, \mathrm{V}_{2}\right)$ under isothermal or adiabatic conditions. The pressure of the gas will fall more rapidly under adiabatic conditions because
(a) $\mathrm{p} \propto \frac{1}{\mathrm{V}}$
(b) $\mathrm{p} \propto \frac{1}{\mathrm{V}^{7/5}}$
(c) $\mathrm{p} \propto \frac{1}{\mathrm{V}^{3/2}}$
(d) $\mathrm{p} \propto \frac{1}{\mathrm{V}^{5/3}}$
Answer Answer: D ✓ checked by 4AB · confidence high
The source book printed A; on checking, D is correct — see the explanation.
Explanation A reversible adiabat obeys pV^γ = constant, with γ = 5/3 for a monatomic gas. p ∝ V^(−5/3) falls faster than the isothermal p ∝ 1/V (d).
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