At a constant temperature liquid `'A'` has vapour pressure of `170 mm Hg` and liquid `'B'` has vapour pressure of `280 mm Hg`. A solution of the two at the same temperature in which mole fraction of `A` is `0.7` has a total vapour pressure of `376 mm`. Identify whether the solution process is Endothermic or Exothermic ?

Answer

Endothermic

Explanation

`P_(T)=0.7xx170+0.3xx280`
(Theo.)
`=203 mm Hg`
But `P_(T)=376mm Hg`
(obsed)
`because P_(T_("obsed"))gtP_(T_("Theo"))`
`therefore` solution shows `(+) ve` deviation which means `DeltaH_("mix")gt0`
or solution is endothermic.
`therefore` Heat will be absorbed in the formation of solution.