Question

Assuming that water vapour is an ideal gas, the internal energy change `(Delta U)` when 1 mol of water is vapourised at 1 bar pressure and `100^(@)C`, (Given : Molar enthalpy of vapourisation of water at 1 abr and 373 K = 41 kJ `mol^(-1)` and `R = 8.3 J mol^(-1)K^(-1)` will be) :-
A. ` 41.00kJ" "mol^(-1)`
B. `4.100kJ" "mol^(-1)`
C. `3.7904kJ" " mol^(-1)`
D. `37.904kJ" "mol^(-1)`

Answer 1

Correct Answer - D
`DeltaU=DeltaH-DeltanRT`
`=41000-1xx3.314xx373`
`=37898.878J" "mol^(-1)`
`=37.9 kJ" "mol^(-1)`