Question

From the colligative properties of solution, which one is the best method for the determination of molecular weight of proteins and polymers?

• A. Osmotic pressure
• B. Lowering in vapour pressure
• C. Lowering in freezing point
• D. Elevation in boiling point

Answer 1

Answer: (A)

Osmotic pressure

Answer 2

Osmotic pressure is the best method for the determination of molar mass of proteins and polymers.Because a small amount of solute will produce a much larger change in this quantity than in the boiling point, freezing point, or vapor pressure. even a 106 molar solution would have a measurable osmotic pressure. Molecular weight determinations are very frequently made on proteins or other high molecular weight polymers. These substances, owing to their large molecular size, tend to be only sparingly soluble in most solvents, so measurement of osmotic pressure is often the only practical way of determining their molecular weights.