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Question
An ideal gas is allowed to expand against a constant pressure of 2 bar from 10 L to 50 L in one step. Calculate the amount of work done by the gas. If the same expansion were carried out reversibly, will the work done be higher or lower than the earlier case? (Given that 1 L bar = 100 J)
Solution
We know that the amount of work done = – pextΔV
On substituting the values in the formula, we get,
– 2bar × (50 – 10) L = – 80 L bar
According to the described problem, 1 L bar = 100 J
Therefore, – 80 L bar = (– 80 × 100) = – 8000 J
= – 8 kJ, which is the amount of work done
The significance of the negative sign states that the work is done in the surroundings of the system. In the case of reversible expansion, the work done will be more.
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