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Question:

A diatomic gas with rigid molecules does 10J of work when expanded at constant pressure. What would be the heat energy absorbed by the gas, in this process?

35J

25J

40J

30J

Solution:

The correct option is A (35J)
For a diatomic gas, Cp = (7/2)R
Since gas undergoes isobaric process ⇒ ΔQ = nCpΔT
Also, ΔW = nRΔT = 10J (given)
∴ ΔQ = n(7/2)RΔT = (7/2)(nRΔT) = 35J