Why does 1 mol of sodium chloride depress the freezing point of 1 kg of water almost twice as much as 1 mol of glycerin?
Reason for the difference in freezing point depression:
1. Sodium chloride (NaCl) is an **electrolyte**. It dissociates completely into two ions (Na⁺ and Cl⁻) when dissolved in water. This increases the number of particles in solution, which causes a greater freezing point depression.
- For NaCl: 1 mol of NaCl produces 2 moles of ions (Na⁺ and Cl⁻), so the number of particles is 2 times that of the solute.
2. Glycerin (C3H8O3) is a **nonelectrolyte**. It does not dissociate and remains as individual molecules in solution, meaning 1 mol of glycerin results in only 1 mole of particles in solution.
Freezing point depression depends on the number of particles in solution, as described by the formula:
ΔT_f = i * K_f * m
Where:
- ΔT_f is the freezing point depression,
- i is the van 't Hoff factor (number of particles),
- K_f is the freezing point depression constant of the solvent (water),
- m is the molality of the solution.
Since NaCl dissociates into 2 particles (i = 2) while glycerin does not dissociate (i = 1), the freezing point depression for NaCl is nearly twice that of glycerin.
