1 kg of air at the initial temperature T1 = 900K Consider a piston-cylinder device containing m = and pressure P = 895 kPa (state 1). The ambient temperature and pressure are maintained at T(e) = 300K and P(e) = 100 kPa. The air expands in a reversible adiabatic process until the air pressure reaches the ambient pressure Pe) (the intermediate state 2). Subsequently, the system undergoes an isobaric process until it reaches the dead state DS.

Image below Question : Consider an alternative process 1 → 2′ → DS in which the air first expands in a reversible adiabatic process until the air temperature reaches the ambient temperature value, T2′ =T(e)(state2′),andthenitundergoesisothermalcompressiontilltheairpressurereachesthe ambient pressure P(e). Assuming that the isothermal compression is slow and without friction, answer the following questions: • Is the process 1 → 2′ → DS reversible or irreversible? Why? • What is the value of useful work performed in this process?