Question

Vapour pressure of chloriform `(CHCI_(3))` and dichloromethane `(CH_(2)CI_(2))` at `25^(@)C` are 200 mm Hg and 41.5 mm Hg respectively. Vapour pressure of solution obtained bu mixing 25.5 g of `CHCI_(3)` and 40.0g of `CH_(2)CI_(2)` at the same temperature will be (Mlecular mass of `CHCI_(3)=1199.5` u and molecular mass of `CH_(2)CI_(2)=85u`
A. 173.9 mm Hg
B. 615.0 mm Hg
C. 347.9 mm Hg
D. 90.63 mm of Hg

Answer 1

Correct Answer - d
`P_(CHCI_(3))^(@)=200 mm Hg. P_(CH_(2)CI_(2))^(@)=41.5 mm Hg`
Moles of `CHCI_(3)`
`("Mass")/("Molecular weight")=((25.5g))/((119.5g mol^(-1)))=0.213 mol`
Moles of `CH_(2)CI_(2)=((40g))/((85gmol^(-1)))=0.470 mol`
`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_(CHCI_(3))^(@)X_(CHCI_(3))+P_(CH_(2)CI_(2))^(@)X_(CH_(2)CI_(2))`
=`200xx0.31+41.5xx0.69
=62+28.63=90.63 mm of Hg