Question

Which colligative property is used to determine the molar mass of proteins?

• A. Osmotic pressure
• B. Elevation in boiling point
• C. Relative lowering of vapour pressure
• D. Depression in freezing point

Hint:

Osmotic pressure is the "go-to" for macromolecules because it yields measurable signals at room temperature.

Answer 1

The Correct Option is A

Step 1: Concept
Colligative properties depend on the number of solute particles. While all four can theoretically determine molar mass, some are more suitable for macromolecules like proteins.

Step 2: Analysis
Proteins have high molar masses, meaning their molal concentrations are very low even at reasonable mass concentrations. This results in extremely small changes for elevation in boiling point or depression in freezing point, which are difficult to measure accurately. Furthermore, high temperatures can denature proteins.

Step 3: Reasoning
Osmotic pressure measurements are carried out at room temperature and produce relatively large, easily measurable values even for very dilute solutions of high-molecular-weight polymers and proteins.

Step 4: Conclusion
Due to sensitivity and the preservation of protein structure at room temperature, osmotic pressure is the preferred method. Final Answer: (A)