Question

`CsOH +HCI rarr CsCI +H_(2)O, DeltaH =- 13.4 kcal mol^(-1)……….(i)`
`CsOH +HF rarr CsF +H_(2)O, DeltaH =- 16.4 kcal mol^(-1) ………(ii)`
Calculate `DeltaH` for the ionisation of `HF` in `H_(2)O`.
A. `3.0 kcal`
B. `-3.0 kcal`
C. `6.0 kcal`
D. `0.3 kcal`

Answer 1

i. `H^(o+) +overset(Theta)OH rarr H_(2)O DeltaH_(1) = - 13.4 kcal`
ii. `overset(Theta)OH +HF rarr H_(2)O +F^(Theta) DeltaH_(2) =- 1.6 kcal`
iii. `HF rarr H^(o+) +F^(Theta) DeltaH_(3) = ?`
`DeltaH_(3) = DeltaH_(2) - DeltaH_(1)`
`=- 16.4 - (-13.4) =- 3.0 kcal`