An aqueous solution containing 28% by mass of a liquid A (molecular mass = 140) has a vapour pressure of 160 mm at `37^(@)C`. Find the vapour pressure of pure liquid A (the vapour pressure of water at `37^(@)C` is 150 mm)

Answer

0.448 bar

Explanation

Moles of liquid A `= (28)/(140) = 0.2`
Moles of water ` =(72)/(18) = 4.0`
Mole fraction of liquid `A, x_(i) = (0.2)/(0.2+4.0) = 0.048`
Mole fraction of water ` , x_(w) = 1.0-0.048 = 0.952`
`0.210 = p_(l)^(@) x_(l) + p_(w)^(@) x_(W)`
`0.210 = p_(l)^(@) xx 0.048 + 0.198 xx 0.952`
`p_(l)^(@) = (0.210 - 0.198 xx 0.952)/(0.048) = 0.448` torr.