Question

In comparison to a 0.01 M solution of glucose, the depression
in freezing point of a 0.01 M MgCl₂ solution is ....... .
(a) the same (b) about twice
(c) about three time (d) about six times

Answer 1

To a 0.01 M solution of glucose, the depression

in freezing point of a 0.01 M MgCl₂ solution is answer

(a) the same

Answer 2

In comparison to a 0.01 M solution of glucose, the depression in freezing point of a 0.01 M MgCl₂ solution is :

• Depression in freezing point is given as

∆Tf = i × m × Kf

where i = van't Hoff factor

m = molality of solution

Kf = Freezing constant

• We are also given that molality is same.

• Kf is same as both compound have same solvent i.e water.

• Therefore, we can say that ∆Tf depends only on van't Hoff factor.

• For MgCl₂, i = 3 as it dissociates into 3 ions.

• For glucose, i = 1 as it does not undergoes dissociation.

• Hence, Depression in Freezing point for MgCl₂ is three times that of glucose.