Question

Which has the highest boiling point?

A) 0.1 M Na2SO4

B) 0.1 M glucose, C6H12O6

C) 0.1 M MgCl2

D) 0.1 M Al(NO3)3

Answer 1

As, the concentrations of all the substances in aqueous solution is same the increase in boiling point due to dissolution of the substances in water is directly proportional to Vanthoff factor , i.

Vanthoff factor is determined by numbers of ions produced from each compound in water.

Na2SO4 = 2 Na⁺ + SO4-2

The numbers of ions produced is 3 and Vanthoff factor is 3

Glucose can not ionise as it is not an electrolyte. Hence Vanthoff factor is 1.

MgCl2= Mg+2 + 2Cl- , it produces 3 ions and Vanthoff factor is 3

Al(NO3)3= Al+3 + 3NO3-

Vanthoff factor is 4.

As Al(NO3)3 has the highest Vanthoff factor, the elevation o f boiling point of its solution is maximum among the four. And ii has the highest boiling point.