Question

Determine the value of `DeltaH` and `DeltaU` for the reversible isothermal evaporation of `90.0g` of water at `100^(@)C`. Assume that water behaves as an ideal gas and heat of evaporation of water is `540 cal g^(-1) (R = 2.0 cal mol^(-1)K^(-1))`.

Answer 1

`{:(,Water,hArr,Vapour,),(Mol e b ef o re evapo ration,90//18=5,,0,):}`
The evaporation of `5 mol e` of water takes place reversibly and isothermally into vapours.
Thus, heat give at constant pressure
`DeltaH=` heat of evaporation `xx` amount evaporated
`DeltaH=540xx90=48600cal`
Also `DeltaH=DeltaU+DeltanRT`
`DeltaU=48600-5xx1xx2xx373`
`=486003730`
`DeltaU=44870cal`