Question

Heat of neutralization of $CsOH$ with all strong acid is $13.4\, kcal \, mol ^{-1}$. The heat released on neutralization of $CsOH$ with $HF$ (weak acid)is $16.4\, kcal\, mol ^{-1} . \Delta H^{\ominus}$ of ionization of $HF$ is

• A. $3.0\, kcal$
• B. $-3.0\, kcal$
• C. $6.0\, kcal$
• D. $0.3\, kcal$

Answer 1

Answer: (B)

$H ^{\oplus}+\overset{\ominus}{ O}H \longrightarrow H _2 O \,\,\, \Delta H_1=-13.4\, kcal$
$\overset{\ominus}{ O}H + HF \longrightarrow H _2 O + F ^{\ominus} \,\,\,\Delta H_2=-16.4 \, kcal$
$HF \longrightarrow H ^{\oplus}+ F ^{\ominus} \,\,\,\Delta H_1=?$
$\Delta H_3=\Delta H_2-\Delta H_1=-16.4-(-13.4)=-3.0\, kcal$