Question

A gas undergoes a change of state during which 100J of heat is supplied to it and it does 20J of work. The system is brough back to its original state through a process during which 20 J of heat is released by the gas. What is the work done by the gas in the second process?

Answer 1

`dQ_(1)=dU_(1)+dW_(1)`
`100=dU_(1)+20rArrdU_(1)=80J`
`dQ_(2)=dU_(2)+dW_(2) (therefore dU_(1)=-dU_(2))`
`-20=-80+dW_(2)rArrdW_(2)=60J`