• question_answer In a thermodynamics process, pressure of a fixed mass of a gas is changed in such a manner that the gas releases 20 J of heat and 8J of work is done on the gas. If the initial internal energy of the gas was 30J. The final internal energy will be  A) 18J B) 9J C) 4.5J      D) 36J

 [a] Given $\Delta Q=-20J,$ $\Delta W=-8J$and ${{U}_{1}}=30J$ $\Delta Q=\Delta U+\Delta W$Þ $\Delta U=(\Delta Q-\Delta W)$ Þ $({{U}_{f}}-{{U}_{i}})$= $({{U}_{f}}-30)=-20-(-8)$ Þ${{U}_{f}}=18J$