Question

An aqueous solution containing 28% by weight of a liquid. A molecular mass = 140 has a vapour pressure of 0.210bar at 37 degree Celsius. Calculate the vapour pressure of pure liquid.
Vapour pressure of water at 37°c = 0.198bar

Answer 1

For two miscible liquids,ptotal=Mole fraction of A×pA° + mole fraction of B×pB°Number of moles of A=28140=0.2Liquid B is water, its mass is 100−28=72Number of moles of B=7218=4 Total number of moles=0.2+4=4.2and, ptotal=160 mmpB°=150 mmSo, 160=0.24.2×pA°+4.04.2×150or, pA°=17.15×4.20.2=360.15 mm