When 1 g-equivalent of strong acid reacts with strong base, heat released is 13.5 kcal. When 1 g-equ — Thermodynamics and Thermochemistry Chemistry Question
Question
When 1 g-equivalent of strong acid reacts with strong base, heat released is 13.5 kcal. When 1 g-equivalent $\text{H}_2\text{A}$ is completely neutralized against strong base, 13 kcal is released. When 1 g-equivalent $\text{B(OH)}_2$ is completely neutralized against strong acid, 10 kcal heat is released. What is the enthalpy change when 1 mole of $\text{H}_2\text{A}$ is completely neutralized by $\text{B(OH)}_2$.
💡 Solution & Explanation
Heat of ionization for $\text{H}_2\text{A} = 13.5 - 13 = 0.5\text{ kcal/eq}$. Heat of ionization for $\text{B(OH)}_2 = 13.5 - 10 = 3.5\text{ kcal/eq}$. Neutralizing 1 eq of both involves strong-strong heat minus both ionizations: $-13.5 + 0.5 + 3.5 = -9.5\text{ kcal/eq}$. Since 1 mole of $\text{H}_2\text{A}$ contains 2 equivalents, total heat = $2 \times (-9.5) = -19\text{ kcal}$.