Question

The freezing point of a 1.00 molal aqueous solution of calcium chloride (CaCl2) is lower than the freezing point of a 1.00 molal aqueous solution of ethylene glycol (C2H6O2). Why are the freezing points of the two solutions different?

Answer 1

Answer:

The calcium chloride is an electrolyte salt, so the frezzing point of solution must be higher than ethylene glycol.

Explanation:

This is the colligative property for this question: Frezzing point depression

ΔTf = Kf · molal · i

ΔTf = T° fussion solvent pure - T° fussion solution

As both solutions are the same in molality and the solvent is water, the formula stands the same but the Calcium Chloride is a salt which is dissociated in water like this:

CaCl₂ → Ca²⁺  + 2Cl⁻

We have 3 moles of ions, so this value modiffy the formula with the Van't Hoff Factor (number of ion particles per individual molecule of solute).

Ethyleneglycol  is a non-electrolytic organic compound (It is often used 1 as the i).

Let's see the formula in both:

0° - T° fussion solution = Kf · molal · 3 → CaCl2

0° - T° fussion solution = Kf · molal · 1 → C2H6O2