Question

A solution contains 18 g glucose in 500 g HOH .calculate the vapor presser of the solution at 60 C

Answer 1

Vapor pressure of water(pure solvent) at 60^oC (P0) =149.4torr

Vapor pressure of glucose solution (containing non-volatile solute) (P) is ?

Relative lowering in vapor pressure of a solution containing non-volatile solute is equal to mole fraction of the solute.

This is according to Raoult's law.

Number of moles of solute glucose = it's given mass/its molecular mass

=18g/180g/mol

=10mol

Number of moles of solvent water =it's given mass/molecular mass

=500g/18g/mol

=27.77mol

Mole fraction of glucose=10mol/(10+27.77)mol

According to Raoults law:

P0-P/P0. = 10/37.77

(149.4torr-P/149.4torr)=10/37.7

On simplification: