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

Options

A. `205mm`
B. `2.05mm`
C. `1.05mm`
D. `105mm`

Answer

4

Explanation

According to Raoult's law for liquid mixtures.
`P=P_(A)+P_(B)`
`P=P_(A)^(@)xx((W_(A))/(M_(A)))/((W_(A))/(M_(A))xx(W_(B))/(M_(B)))+P_(B)^(@)xx((W_(B))/(M_(B)))/((W_(A))/(M_(A))+(W_(B))/(M_(B)))`
`P=145=P_(A)^(@)xx((64)/(128))/((64)/(128)+(36)/(18))+155xx((36)/(18))/((64)/(128)+(36)/(18))`
`P_(A)^(@)=105mm`