ThermochemistryHard

Question

When 1 g equivalent of strong acid reacts with strong base, the heat released is 13.5 kcal. When 1 g equivalent H2A is completely neutralized against strong base, 13 kcal is released. When 1 g equivalent B(OH)2 is completely neutralized against strong acid, 10 kcal heat is released. What is the enthalpy change when 1 mole of H2A is completely neutralized by B(OH)2?

Options

A.−27 kcal
B.−10 kcal
C.−20 kcal
D.−19 kcal

Solution

For H2A, enthalpy of ionization = $2 \times (13.5 - 13) = 1$ kcal/mol

For B(OH)2, enthalpy of ionization = $2 \times (13.5 - 10) = 7$kcal/mol

∴ Required $\Delta H = 2 \times 13.5 - 1 - 7 = - 19\text{ kcal}$

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