Question

Why does sodium chloride freeze at lower temperature than water?

Answer 1

Explanation:

NaCl is ionic whereas water is covalent

Ions are easily cooled and heated

But in case of water, molecules are present and hence molecules take some extra amount of heat to get heated and vice-versa

Extra heat is required by the molecules to break the intermolecular forces of attraction but in case of ions electricity does the same work

It can also be due to some impurity

Answer 2

On adding a non-volatile solute like NaCl to water, the vapor pressure is lowered. The vapor pressure of this solution becomes equal to that of pure solid solvent which is the freezing point of the solution occurs at a lower temperature. Thus freezing point of NaCl solution is lower than that of pure solvent.