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:

A and C only

The answer is (2) A and C only.

Let's look into each statement in more detail:

A. If dissolution process is endothermic, solubility increases with an increase in temperature:
This statement is generally true. When the dissolution process is endothermic, it means that energy is required for the solute particles to break apart and mix with the solvent. Increasing the temperature provides more thermal energy to the system, making it easier for the solute to overcome the energy barrier and dissolve in the solvent. As a result, the solubility tends to increase with higher temperatures.

B. If dissolution process is endothermic, solubility decreases with an increase in temperature:
This statement is incorrect and contradicts the general trend. Endothermic processes are typically associated with an increase in solubility at higher temperatures.

C. If dissolution process is exothermic, solubility decreases with an increase in temperature:
This statement is generally true. In exothermic processes, the dissolution of the solute releases heat. Increasing the temperature can disrupt the equilibrium by providing additional energy to the system. This may shift the equilibrium toward the reverse reaction (precipitation), resulting in a decrease in solubility.

D. If dissolution process is exothermic, solubility increases with an increase in temperature:
This statement is incorrect. Exothermic processes usually exhibit a decrease in solubility at higher temperatures due to the reasons mentioned in statement C.

Therefore, the correct answer is 2. A and C only.