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.
In a nearly saturated solution, which of the following statements are correct?
A. If dissolution process is endothermic, solubility increases with increase in temperature
B. If dissolution process is endothermic, solubility decreases with increase in temperature
C. If dissolution process is exothermic, solubility decreases with increase in temperature
D. If dissolution process is exothermic, solubility increases with increase in temperature
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → A and C only
In a nearly saturated solution, dissolution is in dynamic equilibrium (solute + solvent ⇌ solution), so Le Chatelier’s principle decides how the solubility changes with temperature.
(A) If dissolution process is endothermic, solubility increases with increase in temperature — True. Heating favours the heat-absorbing (dissolving) direction.
(B) If dissolution process is endothermic, solubility decreases with increase in temperature — False. It is the opposite of (A).
(C) If dissolution process is exothermic, solubility decreases with increase in temperature — True. Heating shifts a heat-releasing equilibrium back, away from dissolving.
(D) If dissolution process is exothermic, solubility increases with increase in temperature — False. It is the opposite of (C).
NCERT (2026-27 edition):
Effect of Temperature
