Question

Out of 0.1 molal aqueous solution of glucose and 0.1 molal aqueous solution of KCl, which one will have higher boiling point and why?

Answer 1

Hint:. To solve this question firstly we should know what boiling point is and on what property the boiling point of a compound depends on. Knowing these two points will help us answer this question within no time.

Complete step by step answer:
Boiling point is the temperature at which the pressure exerted on the liquid surface from surroundings is equal to the pressure exerted by the vapour of the liquid. KCl is an ionic compound and the glucose is a covalent compound.
-Firstly it is more important to know what 0.1 molal of aqueous solution is.

Formula to calculate molarity:
Molarity = $\dfrac{{moles{\text{ }}of{\text{ }}solute\;}}{{kilogram{\text{ }}of{\text{ }}solvent}}$
So, 0.1 molal means 0.1 moles of solute in 1kg of solvent.

- The boiling point of 0.1molal of KCl and glucose:
Boiling point can be also considered as the colligative property. We know that colligative property directly depends on the number or amount of constituent ions.
Since KCl is ionic in nature, it gives out more ions than glucose. Glucose has a bit more complex structure than KCl. If we compare the number of constituent ions produced by KCl and glucose in 1Kg of solvent. The number of constituent ions produced by KCl is more than that is produced by glucose.
Thus, the boiling point of 0.1 molal aqueous solution of KCl is more than 0.1 molal of glucose.

Note: In this question we account for the boiling point of given compounds in means of colligative property, because we are asked to compare the boiling point of 0.1molal quantity of two compounds. As colligative property directly depends on the number or amount of constituent ions.