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.

When osmotic pressure and temperature for two solutions are same, equal volumes of solution would contain same number of:

Moles of solute

The correct 1. Moles of solute.

The osmotic pressure of a solution is a measure of the pressure that must be applied to a pure solvent to prevent the flow of solvent molecules into the solution through a semipermeable membrane. The osmotic pressure of a solution is directly proportional to the number of solute molecules in the solution and inversely proportional to the volume of the solution. Therefore, when two solutions have the same osmotic pressure and temperature, they must contain the same number of solute molecules.

So the answer is 1. Moles of solute.