Question

A closed system receives 200 kJ of heat at constant volume. It then rejects 100 kJ of heat while it has 50 kJ of work done on it at constant pressure. If an adiabatic process can be found which will restore the system to its initial state, the work done by the system during this process is

• A. 100 kJ
• B. 50 kJ
• C. 150 kJ
• D. 200 kJ

Answer 1

The correct option is C 150 kJ

Sol: (c)
$Q_{A\to B}=△U_{A\to B}=+200kJ△U_{B\to C}=△Q_{B\to C}-△W{}_B\to c=-100kJ-(-50kJ)=-50kJ△U_c\to A=-△U_{A\to B}+△Q_{B\to C}\therefore △U_{cycle}=0=-200kJ-50kJ=-150kJ$