Vapour pressure of chlolfom `(CHCI_(3))` and dichloromethane `(CH_(2) CI_(2))` at 298 K are 200 mm Hg and 415 mm Hg respectively. Calculate the vapour pressure of the solution prespared by miximng 25 g of `CHCI_(3)` and 45 g of `CH_(2) CI_(2)` at 298 K. Also find the mole fraction of `CHI_(3)` in the vapour phase .

Explanation

Moles of `underset((A))(CHCl_3)=(25.5)/(119.5)`
= 0.213
`underset((B))(CH_2Cl_2)=40/85`
= 0.470
Mole fraction of A `= (0.213)/(0.213+0.470)`
`=0.3118`
Mole fraction of `B = 1 -x_A`
` = 1- 0.3118`
`=0.6882`
`P_A=P_A^@x_A`
`= 200 xx0.3118`
`= 62.36`
`P_B=P_B^0x_B`
`=415 xx0.6882`
`= 285.603`
`P_("sol"^(4))=P_A+P_B`
= 62.36 + 235.603
= 347.96
(ii) `y_(CHCl_3)=P_A/(P_A+P_B)`
`= (62.36)/(347.96)`
= 0.179
`y_(CH_2Cl_2)=P_B/(P_A+P_B)`
`= (285.603)/(347.96)`
= 0.82