Calculate the vapour pressure lowering caused by addition of `50g` of sucrose (molecular mass `= 342)` to `500g` of water if the vapour pressure of pure water at `25^(@)C` is `23.8 mm Hg`.

Explanation

According to Raoult's law,
`(p_(0)-p_(s))/(p_(0)) = (n)/(n+N)` or `Deltap = (n)/(n+N) p_(0)`
Given: `n =(50)/(342) =0.146, N = (500)/(18) = 27.78` and `p_(0) = 23.8 mm Hg`
Substituting the values in the above equations,
`Deltap = (0.146)/(0.146 +27.78) xx 23.8 = 0.124 mm Hg`