Question

Vapour presure of chloroform `(CHCI_(3))` and dichloromethane `(CH_(2)CI_(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 or `CHCI_(3)` and 40g of `CH_(2)CI_(2)` at the same temperature will and 40 g of `CH_(2)CI_(2)` at the same temperature will be `(("Molecular mass of" CHCI_(3) = 119.5 u` and molecular mass `0 CH_(2)CI_(2) = 85 u)
A. 173.9 mm Hg
B. 615.0 mm Hg
C. 347.9 mm Hg
D. 90.64 mm Hg

Answer 1

Correct Answer - D
`p^(o)CHCI_(3) = 200 mm Hg, p^(o)CH_(2)CI_(2) = 41.5 mm Hg`
`"Moles of "CHCI_(3) "Mass"/"Molecular mass"=25.5/119.5 = 0.213`
`"Moles of " CH_(2)CI_(2) = 40/85 = 0.470`
`X_(CHCI_(3)) = 0.213/(0.213 + 0.470) = 0.31`
`X_(CH_(2)CI_(2))= 0.470/(0.213 + 0.470)=0.69`
`P_(T) = P^(o_(CHCI_(3))) X_(CHCI_(3)) + P^(o_(CH_(2)CI_(2)))X_(CH_(2)CI_(2)`
`P_(T) = 200 xx 0.31 + 41.5 xx 0.69 `
`P_(T) = 62 + 28.63 = 90.63`