Assuming that water vapour is an ideal gas, the internal energy change `(DeltaU)` when 1 mole of water is vaporised at `1 ba r` pressure and` 100^(@)C, (` given`:` molar enthalpy of vaporization of water `41kJ mol^(-1)` at `1 ba r` and `373 K ` and `R=8.3 J mol^(-1)K^(-1))` will be `:`

Options

A. `4.100kJ mol^(-1)`
B. `3.7904kJ mol^(-1)`
C. `37.904kJ mol^(-1)`
D. `41.00kJ mol^(-1)`

Answer

C

Explanation

`H_(2)O_((l))overset("vaporisation")rarr H_(2(g))`
`Deltan_(g)=1-0=1`
`DeltaH+Deltan_(g)RT`
`DeltaU=DeltaH-Deltan_(g)RT=41.8.3xx10^(-3)xx373`
`=37.9kJ mol^(-1)`