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Question
The work done on the system in changing the state of a gas adiabatically from equilibrium state A to equilibrium state B is 22.4 J. If the gas is taken from state A to B through another process in which the net heat absorbed by the system is 15.5 cal, then the net work done by the system in the latter case is ______.
( l cal = 4.2 J)
Options
32.4 J
56 J
14.3 J
42.7 J
Solution
The work done on the system in changing the state of a gas adiabatically from equilibrium state A to equilibrium state B is 22.4 J. If the gas is taken from state A to B through another process in which the net heat absorbed by the system is 15.5 cal, then the net work done by the system in the latter case is 42.7 J.
Explanation:
As the work is done on the system,
`Delta`W = - 22.4 J
In an adiabatic process, `Delta` Q = 0
`therefore` `Delta`U = -`Delta`W = 22.4 J
Now, the internal energy is a state function. Thus, it does not depend on the path.
For second case
`Delta`Q = `Delta`U + `Delta`W'
`therefore` `15.5 xx 4.2` = 22.4 =+ `Delta`W'
`therefore` `Delta`W' = 65.1 - 22.4 = 42.7 J
