Four moles of an ideal gas are caused to expand from a volume V1 to a volume V2 = 2V1.
(a) If the expansion is isothermal at the temperature T = 400K, find the work done by the expanding gas.
(b) Find the change in entropy, if any.
(c) If the expansion were reversibly adiabatic instead of isothermal, would the change in entropy be positive, negative, or zero?