When 1 mole of ice at 0∘C and 4.6 mm of Hg is converted to water vapours at a constant temperature and pressure. Find ΔH and ΔU , if the latent heat of fusion of ice is 80 cal/g and latent heat of vaporisation of liquid water at 0∘C is 536 cal/g. The volume of ice in comparison to volume of vapours may be neglected.