Question

The osmotic pressure of dilute solution is directly proportional to the –
A.Diffusion rate of the solute.
B.Ionic concentration.
C.Boiling point
D.Flow of solvent from a concentrated solution.

Answer 1

Hint: Osmotic pressure is the minimum pressure needed to stop the flow or osmosis of solvent molecules through the semipermeable membrane. Osmosis is a special case of diffusion in which solvent molecules migrate from higher concentration of solute molecules to lower concentration of solute molecules.

Complete step by step answer:
As we already know, Osmotic pressure is the external pressure that when applied on the solution to prevent the solvent from moving from higher concentration area to lower concentration area. It is denoted by $\pi $ so that it can be distinguished from the atmospheric pressure P.
Van’t Hoff on the basis of experiments stated that the gas laws which are applicable on gases are also applicable on dilute solutions. So we know the gas equation shows the relation between Pressure, volume, number of moles and temperature of a gas. Since here the pressure (osmotic) = $\pi $
Then we can write-
$ \Rightarrow {\text{pV = nRT}}$ Where V is the volume, R is gas constant and T is Temperature.
Now on transferring the volume V on right side we get,
$ \Rightarrow {{\pi = }}\dfrac{{{\text{nRT}}}}{{\text{V}}}$
Now we know that $\dfrac{{\text{n}}}{{\text{V}}}$ represents concentration C so on applying this we can write-
$ \Rightarrow {{\pi = CRT}}$
Then we can write at constant temperature,
$ \Rightarrow {{\pi }} \propto {\text{C}}$

Hence the correct option is B.

Note:
Osmotic pressure is a colligative property just like elevation in boiling point and depression in freezing point. Its uses are-
It is the best way to the molecular mass of the solute.
It is used to calculate the molecular mass of biomolecules and polymers with high molecular masses at room temperature as they are unstable at high temperatures.
It is also used in desalination of seawater to make the sea water drinkable.