At `25^(@)C, 1 mol` of A having a vapour pressure of 100 torr and 1 mole of B having a vapour pressure of 300 torr were mixed. The vapour at equilibrium is removed, condensed and the condensate is heated back to `25^(@)C`. The vapour now formed are again removed, recondensed and analyzed. what is the mole fraction of A in this condensate?

Answer

`x_(a)=0.1`

Explanation

`"n"_("A")" ""P"_("A")^(0)=100"torr"`
`"n"_("B")" ""P"_("B")^(0)=100"torr"`
`"X"_("A")="X"_("B")=1//2`
`"Y"_("A")=("P"_("A"))/("P"_("T"))=(1//2xx100)/(1//2xx100+1//2xx300)`
`=(1)/(4)`
mole fraction A in condensate
`"X'"_("A")="Y"_("A")=(1)/(4)" ""X'"_("B")="Y"_("B")=3//4`
`"Y'"_("A")=(1/4xx100)/(1/4xx100+3/4xx300)=0.1`
mole fraction of A in `2^(nd)` condensate
`"X'"_("A")" ""X''"_("B")=0.9`