Question

Why is the unit molality preferred over molarity?

Answer 1

1. Molality is preferred over molarity in many cases because molality is independent of temperature, while molarity changes with temperature.
2. Molarity is defined as moles of solute per litre of solution, and since volume expands or contracts with temperature, molarity is not constant when temperature changes.
3. On the other hand, molality is defined as moles of solute per kilogram of solvent, which is mass-based and remains unchanged with temperature.
4. Therefore, molality is more reliable for temperature-sensitive calculations, such as those involving colligative properties (boiling point elevation, freezing point depression, etc.).