Question

Two volatile liquide A and B are mixed in mole ratio 1:3, to form an ideal liquid solution Vapour pressure of pure. A and B are 600 torr and 200 torr. Volume of container for vapour is 76 litre. `(R= 1//12" " "litre" " "atm//K//"mole")`
The minimum number of distillation steps required, so that mole fraction of A become `0.9` in distillate.
A. `1`
B. `2`
C. `3`
D. `4`

Answer 1

Correct Answer - C
`Y_(A_(1)) = 0.5 = X _(A_(2))`
`Y_(A_(2)) = 0.5 xx 600 + 0.6 xx 200 = 400` torr
`Y_(A_(2)) = (0.5xx600)/(400) = (3)/(4) = X_(A_(2))`
` Y_(A_(3)) = (3)/(4) xx 600 +(1)/(4) xx 200 = 500` torr
` Y_(A_(3))xx 500 = (3)/(4) xx 600 `
`Y_(A_(3)) xx (9)/(10) = X_(A_(4))`