Question

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

• A. $9J$
• B. $27J$
• C. $18J$
• D. $12J$

Answer 1

The correct option is C $18J$

$dQ=-20JdW=-8J{V}_i=30JdQ=dV+dWdQ=(V_f-V_i)+dW-20=(V_f-30)-8-12=V_f-30V_f=18$

$\therefore$ Final internal energy=$18J$