_ 3 moles of an ideal gas undergo an expansion from a volume of 20 liters to a volume of 30 litres (1L = 0.001 m3). The temperature of the initial and final states are both 20C. (a) Calculate the entropy change of the gas if this process is a reversible isothermal expansion (b) What was the entropy change of the gas's surroundings in (a)? How much did the entropy of the universe change as a whole? (c) Calculate the entropy change of the gas if this process is an irreversible free expansion (adiabatic + isothermal). (d) What was the entropy change of the gas's surroundings in ()? How much did the entropy of the universe change as a whole