The value of neutralization enthalpy —57.3 Kj is appropriate for all strong acid base:
The neutralization reaction of given acid and base
HCl (aq) + NaOH (aq) = NaCI (aq) + H2O (l); ∆H a -57.53 Kj
HC1(aq) + KOH (aq) = KCI (aq) + H2O (l); ∆H – -58.28 Kj
HNO3 (aq) + NaOH (aq) = NaNO3 (aq) + H2O (l); ∆H = -57.28 Kj
All strong acid and base are completely ionized in aqueous medium. In the neutralization reaction, only participate H+ and OH– and produce H2O. Other ions remain fire as like as before.
The actual reaction,
H+ (aq) + OH– (aq) = H2O (1), ∆H = -57.3 Kj
For that all strong acid and base have the same initialization heat.
If the acid or base be weak, they do not ionized completely. But they might to be ionized completely before reaction. As a result the energy is needed to ionized the weak acid or base completely. The energy comes from the solution. Fur that neutralization energy of weak base or acid is lower than the strong acid or base.