Two moles of an ideal gas expand from 2 litres to 22 litres against a constant external pressure of 1 atm. Calculate the magnitude of work done by the gas. (Given: 1 litre-atm = 100 J)

2000 J
2200 J
200 J
20 J

Correct answer: 2000 J

Solution

Against constant external pressure the work done by the gas equals P_ext times the change in volume, regardless of the number of moles (moles only matter for internal pressure).

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