The standard enthalpy of neutralization for a strong acid reacting with a strong base is approximate — Thermodynamics and Thermochemistry Chemistry Question

💡 Solution & Explanation

A strict $-57.1 \text{ kJ}$ enthalpy of neutralization reflects the complete formation of water from completely dissociated $H^+$ and $OH^-$ ions. If an acid or base is weak ($CH_3COOH$, $HCN$, $NH_4OH$), it remains predominantly unionized in solution. A fraction of the neutralization energy released must be spent to overcome the enthalpy of dissociation of the weak electrolyte, reducing the net exothermic heat detected.