Question

Two aqueous solutions - 0.1 M NaCl and 0.1 M KNO3 - have the same freezing point. Explain how this observation is consistent with what is known about colligative properties.

Answer 1

1. Depression in Freezing Point Depression is a colligative property.
2. The value of Colligative properties depends upon the concentration of solute in the solvent and not on the type of solute.
3. Isotonic solutions of the solutes those on dissociation gives the same number of ions have same colligative property value.
4. NaCl (aq) Na⁺(aq) + Cl^- (aq) and KNO₃ (aq) K⁺(aq) + NO₃^- (aq).
5. Both NaCl & KNO3 gives the same number of Ions on dissociation and are Isotonic solutions.
6. Hence Having found the same Freezing point for 0.1 M aq.NaCl & 0.1 M aq. KNO3 solution is consistent with the colligative properties.

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