The enthalpy of neutralisation of a strong acid by a string base is `-57.32 kJ mol^(-1)`. The enthalpy of formation of water is `-285.84 kJ mol^(-1)`. The enthalpy of formation of hydroxyl ion is

Options

A. `+ 228.52 KJ//mol`
B. `- 114.26 KJ//mol`
C. `- 228.52 KJ//mol`
D. `+ 114.2 KJ//mol`

Answer

C

Explanation

`H^(+) (aq). + OH^(-) (aq) rarr H_(2)O (l)`
`Delta_(r )H = Delta_(f)H_(H_(2)O) - (Delta_(f)H_((H^(+)(aq))) + Delta_(f)H_((OH^(-))))`
`-57.32 = 285.84 - (0 + Delta_(f)H_((OH^(-)(aq))))`
`Delta_(f)H_(OH^(-)(aq)) = -228.52 KJ//mol`