Question

The method preferred for 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 the best method for the determination of molecular weight of polymers and proteins, since osmotic pressure, though very small, is measurable.

On the other hand, in other colligative properties ($\Delta T_b,\Delta T_f,\Delta p/p^o$), the difference is very small and cannot be measured.

Morever, in osmotic pressure method, heating is not required. While in other methods, heating is required which changes the properties of polymers and proteins.

Hence, the correct option is A.