A piston exerting a pressure of 1 atm rests on the surface of water at 100C . the pressure is reduced to smaller extent and as a result 9g of water evaporates and absorbs 20 kJ of heat. calculate 1.delta H 2. work done on water vapour 3. heat of vapourization 4. delta U Share with your friends Share 6 Vartika Jain answered this Dear Student, w=P∆V∆V=(Volume of vapour-volume of liquid)Volume of vapour >> Volume of liquid, therefore,∆V= Volume of vapourNow, PV=nRTor, V=nRTPTherefore, w=P×nRTP=nRTT=100°C=273+100=373 Kn=918=0.5 molTherefore, w=(0.5)(8.314)(373)=1550.56 J= 1.550 kJ∆U=q+w= 20 kJ +1.55 kJ=21.55 kJ∆H=∆U+P∆V =21.55+1.55=23.1 kJ Heat absorbed by 9 g of water=20 kJHeat absorbed by 18 g of water=20×189=40 kJTherefore, ∆Hvap of water= 40 kJmol-1 3 View Full Answer