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.

Determine the molarity of a solution containing \(4 g\) of \(NaOH\) in \(1 L\)  solution

0.1 M

Given,

\(\text{Weight of NaOH = 4g}\)

\(\text{Molecular weight of NaOH = 40 g}\)

\(\text{Volume of the solution = 1000 mL}\)

Now, we know,

\(Molarity = \frac{\text{Weight of NaOH }}{\text{Molecular weight of NaOH}} × \frac{1000}{\text{Volume in mL}}\)

or, \(Molarity = \frac{4}{40} × \frac{1000}{1000}\)

or, \(Molarity = 0.1 M\)