The enthalpy of neutralisation of a weak acid in 1 M solution with a strong base is `-56.1` kJ `mol^(-1)`/ If the enthalpy of ionization of the acid is 1.5 kJ `mol^(-1)` and enthalpy of neutralization of the strong acid with a strong base is `-57.3` kJ `"equiv"^(-1)`, what is the % ionization of the weak acid in molar solution (assume the acid to be monobasic)?

Answer

20

Explanation

`HA + aq to H_(aq)^(+) + A_(aq)^(-). DeltaH = xkJ mol^(-1)`
`H_(aq)^(+) + OH_(aq)^(-) to H_(2)O_(l) DeltaH =-57.3 kJmol^(-1)`
But `DeltaH=x-57.3 =-56.1` (given)
if no self ionisation of HA occurs of all,
`DeltaH` (ionisation) `=1.5 kJ mol^(-1)`
Hence % ionization in 1 M solution
`=(1.5-1.2)/1.5 xx 100=20`