Question

The osmotic pressure of equimolar solutions of ${\mathrm{BaCl}}_2$, $\mathrm{NaCl}$ and glucose will be in the order:

• A. ${\text{Glucose > NaCl > BaCl}}_{\text{2}}$
• B. ${\text{BaCl}}_2>\text{NaCl > Glucose}$
• C. $\mathrm{NaCl}>{\mathrm{BaCl}}_2>\mathrm{Glucose}$
• D. $\mathrm{NaCl}>\mathrm{Glucose}>\mathrm{Ba}$

Answer 1

The correct option is B

${\text{BaCl}}_2>\text{NaCl > Glucose}$

Explanation for correct option

(B)${\text{BaCl}}_2>\text{NaCl > Glucose}$

Osmotic pressure

• The flow of the solvent from its side to the solution side across a semipermeable membrane can be stopped if some extra pressure is applied on the solution. This pressure that just stops the flow of solvent is called osmotic pressure of the solution.
• Osmotic pressure is a colligative property.
• The expression for osmotic pressure is as follows:-
• $\pi =iCRT$
• Here, $\mathrm{\pi }$ is the osmotic pressure, i, known as the van’t Hoff factor, to account for the extent of dissociation or association, $C$ is the concentration, $R$ is the gas constant, and $T$ is the temperature.
• The dissociation of ${\mathrm{BaCl}}_2$ is as follows:-
• ${\mathrm{BaCl}}_2\to {\mathrm{Ba}}^{2+}+2{\mathrm{Cl}}^{-}$
• So, the value of van't hoff factor is $3$.
• The dissociation of $\mathrm{NaCl}$ is as follows:-
• $\mathrm{NaCl}\to {\mathrm{Na}}^{+}+{\mathrm{Cl}}^{-}$
• So, the value of van't hoff factor is $2$.
• The value of van't Hoff factor for glucose is $1$ because it does not give any ions in the solution.
• Hence, the order of osmotic pressure of equimolar solutions of ${\mathrm{BaCl}}_2$, $\mathrm{NaCl}$ and glucose is as follows:-
• ${\text{BaCl}}_2>\text{NaCl > Glucose}$

Explanation for incorrect option

The order of osmotic pressure of equimolar solutions of ${\mathrm{BaCl}}_2$, $\mathrm{NaCl}$ and glucose is ${\text{BaCl}}_2>\text{NaCl > Glucose}$. Hence, options (A), (C), and (D) are incorrect.

Hence, option (B) is correct. The order of osmotic pressure of equimolar solutions of ${\mathrm{BaCl}}_2$, $\mathrm{NaCl}$ and glucose is ${\text{BaCl}}_2>\text{NaCl > Glucose}$.