MEDIUMMCQ SINGLENEET ChemistryPhysical ChemistryThermodynamics and ThermochemistryPrevious Year Questions

For a sample of perfect gas when its pressure is changed isothermally from pi to pf, the entropy change is given by. (NEET-II 2016)

A.∆S = nR

B.∆S = nR✓ Correct

C.∆S = nRT

D.∆S = RT

Explanation

For an ideal gas undergoing reversible expansion, when temperature changes from Ti to Tf and pressure changes from pi to pf, ∆S = nCp f i T ln T + nR i f p ln p For an isothermal process, Ti = Tf so, ln 1 = 0 ∴ ∆S = nR i f p ln p

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