1.

On the basis of the following thermochemical data :(DeltafG^(@)H_((aq))^(+)=0)H_(2)O(l)rarrH^(+)(aq)+OH^(-)(aq), DeltaH=57.32 kJH_(2)(g)+(1)/(2)O_(2)(g)rarrH_(2)O(l), DeltaH=-286.20 kJThe value of enthalpy of formation of OH^(-) ion at 25^(@)C is

Answer»

`-22.88` kJ
`-228.88` kJ
`+228.88` kJ
`-343.52`kJ

Solution :`H_(2)(G)+(1)/(2)O_(2)(g)rarrH_(2)O(l) , DELTAH=-286.20 kJ`
`DeltaH_(r)=DeltaH_(f)(H_(2)O,l)-DeltaH_(f)(H_(2),g)-(1)/(2)DeltaH_(f)(O_(2),g)`
`-286.20=DeltaH_(f)(H_(2)O(l))`
so, `DeltaH_(f)(H_(2)O,l)=-286.20`
`H_(2)O(l)rarrH^(+)(AQ)+OH^(-)(aq),DeltaH=57.32 kJ`
`DeltaH_(r)=DeltaH_(f)^(@)(H^(+),aq)+DeltaH_(f)^(@)(OH^(-),aq)-DeltaH_(f)^(@)(H_(2)O,l)`
`57.32=0+DeltaH_(f)^(@)(OH^(-),aq)-(-286.20)`
`DeltaH_(f)^(@)(OH^(-),aq)=57.32-286.20=-228.88 kJ`


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