2.11 (a) Derive the equation for the work of reversible isothermal expansion of a van der Waals gas from V1 to V2. (b)A mole of CH4 expands reversibly from 1

to 50 L at 25°C.Calculate the work in joules assuming (1) the gas is ideal and(2) the gas obeys the van der Waals equation. For CH4(g), a =2.283 L2 bar mol-2 and b 0.042 78 L mol-1.