On the basis of the following thermochemical data `:` `(Delta_(f)G^(@)H_((aq.))^(+)=0)`
`H_(2)O_((l))rarr H_((aq.))^(+)+OH_((aq.))^(-),DeltaH=57.32kJ`
`H_(2(g))+(1)/(2)O_(2(g))rarrH_(2)O_((l)),DeltaH=-286.20kJ`
The value of enthalpy of formation of `OH^(-)` ion at `25^(@)C` is `:`

Options

A. `-22.88kJ`
B. `-228.88kJ`
C. `+228.88kJ`
D. `-343.52kJ`

Answer

B

Explanation

`H_(2)O_((l))rarr H_((aq.))^(+)+OH_((aq.))^(-), DeltaH=57.32kJ …..(1)`
`H_(2(g))+(1)/(2)O_(2(g))rarr H_(2)O_((l)), DeltaH=-286.20kJ ...(ii)`
By adding `eqs. (i)` and `(ii)`,
`H_(2(g))+_(1)/(2)O_(2(g))rarr H_((aq.))^(+)+OH_((aq.))^(-), DeltaH=-228.88kJ`
`:' Delta_(f)H^(@) of H_((aq.))^(+)=0`
`:. Delta_(f)H^(@) of OH^(-)=-228.88kJ`