A solutions 16 g of methanol and 90 g of water. The mole fraction of methanol in the solution is :

Options

A. `0.200`
B. `0.549`
C. `0.786`
D. `0.478`

Answer

D

Explanation

p (pentane) `=440` mm Hg
p (hexane)`=120` mm Hg
`x` (pentane)`=(1)/(1+4)=0.2`
`x` (hexane)`=(4)/(1+4)=0.8`
p (pentane)`=0.2xx440=88` mm
p (hexane)`=0.8xx120=96` mm
total vapour pressure `=88+96=184` mm
Mole fraction of pentane in vapour phase
y (pentane) `=(88)/(184)=0.478`