Question

Solute A is a ternary electrolyte and Solute B is non-electrolyte. If 0.1 M solution of solute B produces an osmotic pressure of 2P, then 0.05 M solution of A at the same temperature will produce an osmotic pressure equal to:
a. P
b. 1.5P
c. 2P
d. 3P

Answer 1

Hint: Ternary electrolyte gives three ions during the electrolytic dissociation reaction whereas a non-electrolyte does not give away any ions in such a reaction.

Complete answer:
Let us look at the situation from a different perspective. Solute A here being a ternary electrolyte will dissociate 3 ions here in this system. We are also given that 0.1 M solution of Solute B produces an osmotic pressure of 2P. We need to understand osmotic pressure, it is a threshold or minimum pressure that would have been applied to a pure solvent had it been passing through a membrane via the process of osmosis.
 We are considering this condition to be that of an ideal solution. For the same the formula of osmotic pressure would be given as follows:

$\Pi =i\times M\times R\times T..................Eqn1$

Where,
$\Pi $= Osmotic pressure
 i = Van’t Hoff’s Factor
 M = Molar Concentration of solution
R = Gas constant
T = Temperature in Kelvin

Substituting values in Equation 1 for Solute B, we get

$\begin{align}
  & 2P=i\times (0.1)\times R\times T...............Eqn2 \\
 & \\
\end{align}$
So, again using values of Equation 2 for Solute A, we get

$\begin{align}
  & Pa=i\times (0.05)\times RT \\
 & \\
\end{align}$
Although i which is Van’t Hoff’s factor would be equal to 3, instead of 1 in the previous case. We get

$\begin{align}
  & Pa=3\times (0.05)\times RT...................Eqn3 \\
 & \\
\end{align}$

This essentially means,
Pa (Osmotic pressure for Solute A) = 3P, after combining equation 2 and 3.

Hence the answer is 3P.


Note: A real life example of osmotic pressure coming into play is an excellent example of semi permeable membrane which is inside the shell of an egg. When the shell is removed in the presence of acetic acid, the membrane around the egg demonstrates osmosis phenomenon.