An ideal gas contained in a piston–cylinder device expands isothermally at 80° C from state 1 to state 2.

A. If the expansion process is reversible and 100 kJ of heat is transferred from the surroundings to the gas, determine the increase in entropy (kJ/K) of the gas.

B. What is the P–V work done in this process?

C. If there is 0.5 kg of air in the piston-cylinder device initially at 100 kPa, find the initial and final volumes of the air.