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
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → 0.1 M
Molarity is the number of moles of solute per litre of solution.
Molar mass of NaOH = 23 + 16 + 1 = 40 g mol−1
\( \displaystyle \text{moles of NaOH} = \frac{4\ \text{g}}{40\ \text{g mol}^{-1}} = 0.1\ \text{mol} \)
\( \displaystyle M = \frac{0.1\ \text{mol}}{1\ \text{L}} = 0.1\ \text{mol L}^{-1} \)
NCERT (2026-27 edition):
Expressing Concentration of Solutions – …
