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Question
An ideal gas is allowed to expand against a constant unknown external pressure from 10 L to 50 L in one step. The work done by the gas is −4000 J. Calculate the unknown pressure (in bar).
If the pressure would have been doubled what would happen to the magnitude of work done ? (Given that, 1 L bar=100 J)
An ideal gas is allowed to expand against a constant unknown external pressure from 10 L to 50 L in one step. The work done by the gas is −4000 J. Calculate the unknown pressure (in bar).
If the pressure would have been doubled what would happen to the magnitude of work done ? (Given that, 1 L bar=100 J)
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Solution
The correct option is A 1 ; doubled
Since, 1 L bar=100 J
w=−4000 J=−4000100 L bar =−40 L bar
In this case, as the expansion is against constant external pressure, work done is given as
w = −Pext(V2−V1)
w=−40 L bar
V1=10 L
V2=50 L
putting values, we get
Pext=1 bar
If the pressure doubles work done, magnitude will also be doubled as w∝Pext
Since, 1 L bar=100 J
w=−4000 J=−4000100 L bar =−40 L bar
In this case, as the expansion is against constant external pressure, work done is given as
w = −Pext(V2−V1)
w=−40 L bar
V1=10 L
V2=50 L
putting values, we get
Pext=1 bar
If the pressure doubles work done, magnitude will also be doubled as w∝Pext
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