Question

The enthalpy of neutralisation of oxalic acid by a strong base is $-25.4\, kcal \,mol ^{-1}$. The enthalpy of neutralisation of strong acid and strong base is $-13.7\, kcal\, equiv ^{-1}$. The enthalpy of dissociation of
$H _{2} C _{2} O _{2} \rightleftharpoons 2 H ^{+}+ C _{2} O _{4}^{2-}$ is

• A. $1.0\, kcal \, mol^{-1} $
• B. $2.0 \,kcal \, mol^{-1} $
• C. $18.55 \,kcal \, mol^{-1} $
• D. $11.7\, kcal \,mol^{-1} $

Answer 1

Answer: (B)

$\Delta H=\Delta H_{\text {dissociation }}+\Delta H_{\text {neutalisation }}$
$\therefore \Delta H_{\text {diss }}=\Delta H-\Delta H_{\text {neut }}$
$=-2 \times 13.7-(-25.4)$
$=-27.5+25.4=-2.0\, kcal\, mol ^{-1}$