Gas is contained in a vertical piston-cylinder assembly. The initial volume of the gas is 0.1 m3 and the initial pressure is 500 kPa. The gas undergoes a quasi equilibrium expansion process to a final volume of 0.25 m3. For each case below, determine the work done [kJ] by the gas and sketch the process on a p? Diagram (be sure to label initial and final states, and show process direction):
a. As the piston rises, the pressure remains constant, i.e., p = constant
b. As the piston rises, p? = constant
c. As the piston rises, p?^(1.4) = constant