UPSC Civil Services (Mains), Chemistry optional · 2024 · Paper I

Q3(c)(iv). Final temperature after Joule–Thomson expansion

5 marks
Topic: Thermodynamics
Answered

Question

Estimate the final temperature of one mole of gas at 200.00 atm and 19.0 °C as it is forced through a porous plug to a final pressure of 0.95 atm. Given: the Joule–Thomson coefficient (μJT) of the gas is 0.150 K atm⁻¹.

Answer in brief

T_final = −10.9 °C (262.3 K); the gas cools by 29.9 K.

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Topic notes: the first law of thermodynamics, adiabatic changes, the Joule–Thomson effect and thermochemistry, with every Civil Services, IFoS and Geo-Scientist PYQ →

CoversJoule–Thomson effectJoule–Thomson coefficientisenthalpic expansioninversion temperatureporous plug

All parts of Question 3

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3(c)(ii) Why a tyre gets hot when it is pumped5 marks
3(c)(iii) Pressure of O₂ over NiO at 25 °C5 marks
3(c)(iv) Final temperature after Joule–Thomson expansion5 marks