Define colligative property. Which colligative property is preferred for the molar mass determination of macromolecules?

Question

$W$ g of a non-volatile electrolyte solid solute of molar mass $M\,\text{g mol}^{-1}$ when dissolved in $100\,\text{mL}$ water decreases vapour pressure of water from $640\,\text{mm Hg}$ to $600\,\text{mm Hg}$. If aqueous solution of the electrolyte boils at $375\,\text{K}$ and $K_b$ for water is $0.52\,\text{K kg mol}^{-1}$, then the mole fraction of the electrolyte $(x_2)$ in the solution can be expressed as ___.
(Given: density of water $=1\,\text{g mL}^{-1}$, boiling point of water $=373\,\text{K}$)

Answer 1

Colligative properties are determined solely by the number of solute particles, irrespective of their type. Osmotic pressure is the chosen colligative property for ascertaining the molar mass of macromolecules.
Step 1: Defining Colligative Properties Colligative properties are characteristics of solutions that are dependent solely on the concentration of solute particles, not their chemical identity.

Illustrative Colligative Properties: - Vapor pressure's relative reduction - Elevation of boiling point - Depression of freezing point - Osmotic pressure

Step 2: Rationale for Osmotic Pressure's Preference in Macromolecule Studies - Osmotic pressure ($ \pi = CRT $) exhibits high sensitivity to minor concentrations, rendering it suitable for calculating the molar mass of large molecules such as proteins and polymers. - In contrast to boiling point elevation or freezing point depression, osmotic pressure can be measured at ambient temperatures, thereby avoiding thermal decomposition of macromolecules.

Define colligative property. Which colligative property is preferred for the molar mass determination of macromolecules?

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