Enthalpy of neutralization of acetic acid and sodium hydroxide is less than - 57.1 kj. Explain why ?

Explanation

The enthalpy of neutrazation of acetic acid with sodium hydroxide is less than - 57.1 kj. This is because of the incomplete ioisation of acetic acid. Since acetic acid is a weak acid so its ionisation is not complete in the solution. Therefore, a part of the energy libreated during combination of `H^(+)(aq) and OH^(-) (g)` ions is used for the ionisation of weak acid. Thus, the value of enthalpy of neutralization of weak acid and strong base or strong acid and weak base is always less than - 57.1 kj.