Question

Rank the following aqueous solutions in order of decreasing boiling point and in order of decreasing vapour pressure at 298 K.

i) 0.03 m sucrose

ii) 0.01 m silver nitrate

iii) 0.02 m calcium chloride

Answer 1

Solution :-

The boiling point is the colligative property so when the total particle concentration increases in the solution then it increases the boiling point of the solution

Lets find the total particle concentration of the solution

0.03 m sucrose = 0.03 m because it is non electrolyte

0.01 m silver nitrate (AgNO3) = 0.01 * 2 = 0.02 m because it forms two ions on dissociation

0.02 m calcium nitrate (Ca(NO3)2) = 0.02 * 3 = 0.06 m because it gives 3 ions on dissociation

So the highest boining point solution to lowest boiling point solution order is as follows

0.02m calcium nitrate > 0.03 m sucrose > 0.01 m silver nitrate

The vapor pressure of the solution decreases when the concentration increases

So the order of decreaing vapor pressure is as follows

0.01m silver nitrate > 0.03 m sucrose   > 0.02 m calcium nitrate.