The heat of neutralisation of oxalic acid is `-25.4` kcal `mol^(-1)` using strong base, NaOH. Hence, the enthalpy change of the process, `H_(2) C _(2)O4 hArr 2 H ^(+) + C _(2) O _(4) ^(2-) ` is

Explanation

Oxalic aacid has two ionisable `H ^(o+)` Hence, expected heat of neutratlisatio, if it be haves as a strong acid would have been `=- 13. 7 xx 2 =- 27. 4 kcal mol ^(-1)`
But experimental value `=- 25. 4 ` kcal `mol ^(-1) therefore ` Heat of ionisation `= 2. 0 kcal mol ^(-1)`