Calculate the change in the entropies of the system and the surroundings, and the total change in entropy, when the volume of a sample of argon gas of mass 21g at 298K and 1.50 bar increases from 1.20dm3 to 4.60dm3 in (a) an isothermal reversible expansion, and (b) an adiabatic reversible expansion. Calculate the change in the entropies of the system and the surroundings, and the total change in entropy, when the volume of a sample of argon gas of mass 21g at 298K and 1.50 bar increases from 1.20dm3 to 4.60dm3 in (a) an isothermal reversible expansion, and (b) an adiabatic reversible expansion