Osmotic pressure measurements are less accurate and difficult to carry out. Therefore, this method is not useful for measuring molecular weights. But it is used to find out the molecular weights of polymers, e.g., plastics, proteins, and starch having many monomer units. Knowing the value of the osmotic pressure of a given solution, the molecular weight of the solute can be calculated using van't Hoff equation.
A solution which shows deviation from Raoult's law is called:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → Real Solution
A solution that obeys Raoult’s law over the entire range of concentration is an ideal solution (ΔmixH = 0, ΔmixV = 0). Most solutions show positive or negative deviations from Raoult’s law because the A–B interactions differ from the A–A and B–B interactions; these are non-ideal or real solutions.
“Real solution” in the option is the same as the book’s term non-ideal solution.
NCERT (2026-27 edition):
Non-ideal Solutions
