Vapour presure of chloroform `(CHCl_3)` and dichloromethane `(CH_2Cl_2)` at 25 `""^@C` are 200 mm Hg and 41.5 mm Hg respectively. Vapour pressure of the solution obtained by mixing 25.5 g of `CHCl_3` and 40 g of `CH_2Cl_2` at the same temperature will be
(Molecular mass of `CHCl_3` = 119.5 u and molecular mass of `CH_2Cl_2 = 85` )

Options

A. 173.9 mm Hg
B. 615.0 mm Hg
C. 347.9 mm Hg
D. 285.5 mm Hg

Explanation

(None) : `P_(CHCI_3)^@ = 200 mm Hg, P_(CH_CI_2)^@ = 41.5 mm Hg`
Moles of `CHCl_3 = ("Weight")/("Molecular weight") = (25.5)/(119.5)=0.213`
Moles of `CH_2CI_2 = 40/85 = 0.470`
`X_(CHCI_3)=(0.213)/(0.213+0.470)=0.31`
`X_(CH_2CI_2) = (0.470)/(0.213+0.470) = 0.69`
`P_(Total) = P_(CHCI_3)^@ X_(CHCI_3)+ P_(CH_2CI_2)^@ X_(CH_2CI_2)`
`=200xx0.31+41.5xx0.69`
`= 62+28.63=90.63`