The vapour pressure lowering caused by addition of 100 g of sucrose (molecular mass = 342) to 1000 g of wate,if the vapour pressure of pure water at `25^(@)C` is 23.8mm Hg,is

Options

A. `0.12mm" of Hg"`
B. `0.125mm" of Hg"`
C. `1.15mm" of Hg"`
D. `1.25mm" of Hg"`

Answer

B

Explanation

`n_(C_(12)H_(22)O_(11))=(100)/(342)=0.292mol`
`n_(H_(2)O)=(1000)/(18)=55.5mol`
`" According to Raoult's law, "(Deltap)/(p^(@))=(n)/(n+N)`
`(Deltap)/(23.8)=(0.292)/(0.292+55.5)`
`Delta=0.125mmHg`