In a thermodynamic process, pressure of a fixed mass of a gas is changed in such a manner that the gas release `20 J` of heat and `8 J` of work is done on the gas. If initial internal energy of the gas was `30 J`, what will be the final internal energy?

Explanation

We know that, `dQ=dU+dW`
Since heat is released heat is released by the system, dQ=20J.
and work is done on the gas, `dW=-8J`
`dU=-20-(-8)=-20+8=-12J`
`rArrU_(f)-U_(i)=-12J`
`U_(f)=U_(i)-12=30-12=18J`