An aqueous solution of 2% nonvolatile solute exerts a pressure of 1. 004 bar at the boiling point of the solvent. What is the molar mass of the solute when P_(A) ^(@) is 1.013 bar ?

An aqueous solution of 2% nonvolatile solute exerts a pressure of 1. 0

1.	An aqueous solution of 2% nonvolatile solute exerts a pressure of 1. 004 bar at the boiling point of the solvent. What is the molar mass of the solute when P_(A) ^(@) is 1.013 bar ?
Answer» Solution :VAPOUR pressure of pure WATER at the boiling point. `(P^(0)) =1 atm = 1.013` BAR Vapour pressure of solution `P _(S) = 1. 004` bar `M_(1) = 18 g mol ^(-1)` `M _(2) ` = ? Mass of solute `= W_(2) = 2g` Mass of solution = 100 g Mass of solvent `W_(1) = 98 g` Applying Ranoult.s law for dilute solution `(P ^(0) -P_(S))/(P ^(0)) = (n_(2))/(n _(1) + n _(2)) = (n_(2))/( n _(1))= ((W _(2))/( M _(2)))/( (W _(1))/( M _(2)))` `(P ^(0) -P_(S))/(P ^(0))= (W_(2))/(M _(2)) xx (M_(1))/(W _(1))` `(1.013-1,004)/(1.013) = (W_(2))/(M _(2)) xx (18 mol ^(-1))/(98G) (or)` `M _(2) = (2 xx 18 xx 1. 103)/(98 xx 0.009) = 41.35g mol ^(-1)`