calculate how muc heat must be supplied to evaporate 18g of water at 298 K
Number of moles in 18 g H2O(l) is = 18g/18 g mol-1 = 1mol
ΔvapUo =ΔvapHo − pΔV = ΔvapHo −ΔngRT
ΔvapHo – ΔngRT = 40.66 kJ mol-1 -(1)(8.314 JK-1 mol-1)(373k)(10-3KJ J-1)
ΔvapUo = 40.66 kJ mol-1 – 3.10 kJ mol-1
= 37.56kJ mol