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A litre of dry air at STP expands adiabatically to a volume of 3 litres. If γ = 1.40, the work done by air is: [3¹.4 = 4.6555] [Take air to be an ideal gas]

1. 60.7 J
2. 90.5 J
3. 100.8 J
4. 48 J

Correct answer: 90.5 J

Solution

P1V1 = 1.013e5*1e-3 = 101.3 J. P2V2 = P1V1*(1/3)^0.4 = 101.3*0.644 = 65.3 J. W = (101.3-65.3)/0.4 ~ 90.5 J.

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