An aqueous solution containing liquid `A(M.Wt.=128) 64%` by weight has a vapour pressure of `145mm`. Find the vapour pressure A. If that of water is `155mm` at the same temperature.

Answer

`P_(A)^(0)=105 mm`

Explanation

According to Raoult's law for liquid mixtures `P=P_(A)+P_(B)`
`P=P_(A^(0)x)(w_(A))/(M_(A)/(w_(A)/M_(A)+(W_(B))/(M_(B))))+P_(B^(0))xxM_(B)/(m_(B)/(W_(A)/(M_(A))+(w_(B))/(M_(B))))`
Given that,
`w_(A)=64g w_(H_(2)O)=36g P_(M)=145mm`
`P_(H_(2)O)=155mm M_(A)=128 M_(H_(2)O)=18`
`P=145=P_(A^(0))xx(64)/(128/(64/(128)+(36)/(18)))+(36)/(18/(64/(128)+(36)/(18)))`
`P_(A^(0))=105mm`