Question

The method of choice of determining the molecular weight of a polymer is:

• A. Osmotic pressure
• B. Gas density
• C. Lowering of freezing point
• D. Direct weighing of a single molecule

Answer 1

The correct option is A Osmotic pressure

Osmotic pressure method is best for the determination of molecular weight of polymers and protiens since osmotic pressure though very small, is measurable. On the other hand, in other colligative properties (e.g., $△T_b,△T_p,\frac{\Delta p}{p^o}$ methods), the difference is very small and cannot be measured. Moreover in O.P. method, heating is not required, while in other methods, heating is required which changes the properties of polymer and protiens