Thermodynamics

JEE Main level, single correct, medium

103 of 190

Question 103 of 190

Heat energy of 735J735J is given to a diatomic gas allowing the gas to expand at constant pressure. Each gas molecule rotates around an internal axis but do not oscillate. The increase in the internal energy of the gas will be:

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Answer: (A) 525J525J

For isobaric process and diatomic gas we can write, ΔQ=nCPΔT=735J\Delta Q=n{C}_{P}\Delta T=735J
⇒n7R2ΔT=735J⇒nRΔT=210\Rightarrow n\dfrac{7R}{2}\Delta T=735J \Rightarrow nR\Delta T=210
Now internal energy will be,

ΔU=nCVΔT=n5R2ΔT=52×210\Delta U=n{C}_{V}\Delta T =n\dfrac{5R}{2}\Delta T =\dfrac{5}{2}\times 210
=525J=525J

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