Vapour pressure of pure chloroform `(CHCl_(3))` and dichloromethane `(CH_(2)Cl_(2))` at `25^(@)C` are 200 mmHg and 41.5 mmHg respectively. Vapour pressure of the solution obtained by mixing 25.5 g of `CHCl_(3)` and 40 g of `CH_(2)Cl_(2)` at the same temperature will be :
(Molecular mass of `CHCl_(3)` = 119.5 u and molecular mass of `CH_(2)Cl_(2) = 85u`)

Options

A. 90.92 mm Hg
B. 615.0 mm Hg
C. 347.9 mm Hg
D. 285.5 mm Hg

Answer

A

Explanation

`n_(CHCl_(3))=(25.5)/(119.5)=0.213`
`n_(CH_(2)Cl_(2))=(40)/(85)=0.47`
`P_(T)=P_(A)^(o)X_(A)+P_(B)^(o)X_(B)`
`=200xx(0.213)/(0.683)+41.5xx(0.47)/(0.683)`
= 62.37 + 28.55 = 90.92 .