The vapour pressure above a solution of `50g` acetic acid `(H_(2)H_(3)O_(2)~ in `100.0g H_(2)O (P_(H_(2)O^(0)=23.756` Torr at `25^(0)C)` was `23.40` Torr and in `100.0g C_(6)H_(6) (P_(C_(6)H_(6)^(0)=72.5` Torr at `25^(0)C)` was `70.0` Torr. Assuming `HC_(2)H_(3)O_(2)` to be non-volatile, use these date to discus the intermolecular bonding in `HC_(2)H_(3)O_(2)~.

Answer

We are to dtermine physical state of acetic acid in two solvents :
(a) Acetic acid `(AcOH)` in water (Ac is `CH_(3)-overset(O)overset(||)C-O^(-))`
`P_(H_(2)O^(2)=23.756` Torr , `n_(H_(2)O=(100)/(18)mol`
(23.756-23.40)/(23.40)=(5//60xxi)/(100//18`
`i=1.01
`igt1`
So, dissociation of `CH_(3)COOH` take place in water.
(b) Acetic acid `(AcOH)` in benzenen
`P_(c_(6)H_(6)^(0)=70.0` Torr, `n_(AcOH)=(5)/(m_(AcOH))mol`
By Raoult's laq `(P_(C_(6)H_(6)^(0)-P_("solvent"))/(P_(C_(6)H_(6)^(0))=(n_(AcOH))=(n_(AcOH))/(n_(C_(6)H_(6))`
`(72.5-70.0)/(72.5)=(5)/(m_(AcOH))xx(78)/(100)`
this gives `m_(AcOH)=113.1g "mol"^(-1)`
This value is just double of the theoretical molecular weight `(60.0g "mol"^(-1))`
Thus, there is association of `AcOH` in `C_(6)H_(6)` by intermolecular `H-` bonding
`(##RES_PHY_CHM_V01_XII_C02_E01_312_A01##)`
(We can altternately first determine `'i'` (van't Hoff factor) and then `Y`.