Thermodynamics Question 271

Question: The variation of internal energy (U) with the pressure (P) of 2.0 mole gas in cyclic process abcda. The temperature of gas at c and d are 300 K and 500 K. calculate the heat absorbed by the gas during the process.

Options:

A) 400 R In 2

B) 200 R In 2

C) 100 R In 2

D) 300 R In 2

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Answer:

Correct Answer: A

Solution:

[a] Change in internal energy for cyclic process (ΔU)=0.

For process ab , (P-constant) Wab=PΔV

=nRΔT=400R

For process bc (T-constant) Wbc=2R(300)ln 2

For process cd , (P-constant) Wcd=+400R

For process da , (T-constant) Wda=+2R(500) ln 2 

Net work (AW) =Wab+Wbc+Wcd+Wda

ΔW=400R ln 2

dQ=dU+dW , first law of thermodynamics dQ=400R ln 2.



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