In changing the state of a gas adiabatically from an equilibrium state A to another equilibrium state B, an amount of work equal to 22.3 J is done on the system. If the gas is taken from state A to B via a process in which the net heat absorbed by the system is 9.35 cal, how much is the net work done by the system in the latter case? (Take 1 cal = 4.19 J)
The work done (W) on the system while the gas changes from state A to state B is 22.3 J. This is an adiabatic process. Hence, change in heat is zero. ∴△Q=0 △W=−22.3J (Since the work is done on the system) From the first law of thermodynamics, we have: △Q=△U+△W Where, △U= Change in the internal energy of the gas ∴△U=△Q−△W=−(−22.3J) △U=+22.3J When the gas goes from state A to state B via a process, the net heat absorbed by the system is: △Q=9.35cal=9.35×4.19=39.1765J Heat absorbed, △Q=△U+△W ∴W=△Q−△U =39.1765–22.3 =16.8765J
