(i) Colligative properties are those properties of the solutions which depend upon the number of solute particles present in the solution irrespective of their nature and are relative to the total number of particles present in the solution. Some colligative properties are elevation of boiling point of solvent, depression of freezing point of solvent, etc.

(ii) Molality is the number of moles of solute dissolved in 100g of a solvent. It is represented by m and is used to express concentration of a solution. It can be calculated as:

m=‌

‌ Number of moles of solute ‌

‌ Weight of solvent in grams ‌

×1000