1.

Standard enthaply of vaporisation Delta_(vap)H^(theta) forwater at 100^(@)C is 40.66 kJ mol^(-1). The internal energy of vapourisation of water at 100^(@)C (in kJ mol^(-1)) is :

Answer»

`+ 40.66`
`+ 37.56`
`- 43.76`
`+ 43.76`

Solution :`Delta H = Delta U + Delta n_(g) RT`
`H_(2)O(l) RARR H_(2)O(g)`
`Delta n_(g) = 1, Delta H = 40.66 xx 10^(3) Jmol^(-1)`,
T = 373K
`40660 = Delta U + 1 xx 8.314 xx 373`
`40660 = Delta U + 3101.12`
`Delta U = 40660 - 3101.12`
`= 37.558 Jmol^(-1)`
`= 37. 56 kJmol^(-1)`


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