The heat of neutralization of oxalic acid is -25.4 k.cal. mol−1 using strong base NaOH then the enthaphy change of the process isH2C2O4⇌ 2H++C2O4−2

Oxalic acid has two ionisable H+ hence expected heat of neutralization, If it behaves as a strong acid would have been =−13.7×2=−27.4 k.cal mol−1But experimental value =−25.4 k.cal.mol−1Heat of ionization =27.4−25.4=2k.cal/ mol