The standard enthalpy of neutralization of with is , and the standard enthalpy of neutralization of — Thermodynamics and Thermochemistry Chemistry Question
Question
The standard enthalpy of neutralization of $NH_4OH$ with $HCl$ is $-51.46 \text{ kJ mol}^{-1}$, and the standard enthalpy of neutralization of $NaOH$ with $HCl$ is $-55.90 \text{ kJ mol}^{-1}$. Determine the exact standard enthalpy of ionization of $NH_4OH$ in aqueous medium in $\text{kJ mol}^{-1}$.
💡 Solution & Explanation
The neutralization of a strong acid ($HCl$) and strong base ($NaOH$) intrinsically releases $55.90 \text{ kJ mol}^{-1}$ solely due to the net ionic reaction $H^+ + OH^- \rightarrow H_2O$. For the weak base $NH_4OH$, a fraction of this energy is strictly consumed to completely ionize it into $NH_4^+$ and $OH^-$ prior to bulk neutralization. $\Delta H_{ionization} = \Delta H_{neut}(weak) - \Delta H_{neut}(strong) = -51.46 - (-55.90) = 55.90 - 51.46 = +4.44 \text{ kJ mol}^{-1}$.