Liquids A and B form an ideal solution in the entire composition range. At 350K, the vapor pressure of pure A and pure B are `7xx10^(3)` Pa and `12xx10^(3)` Pa, respectively. The composition of the vapor in equilibrium with a solution containing 40 mole percent of A at this temperature is :

Options

A. `x_(A) = 0.37 , x_(B) = 0.63`
B. `x_(A) = 0.28 , x_(B) = 0.72`
C. `x_(A) = 0.76 , x_(B) = 0.6`
D. `x_(A) = 0.4, x_(B) = 0.6`

Answer

B

Explanation

`p_(A) = p_(A)^(@) xx x_(A)`
` = 7 xx 10^(3) xx 0.4 Pa = 2.8 xx 10^(30 Pa`
` p_(B) = p_(B)^(@) xx x_(B)`
` = 12 xx 10^(3) xx 0.6 Pa = 7.2 xx 10^(3) Pa`.
Composition in vapour phase .
`y_(A) = (p_(A))/(p_("total")) = (2.8xx 10^(3))/(2.8xx10^(3) + 7.2 xx 10^(3)) = 0.23`
`y_(B) = 1-0.28 = 0.72`