Match List-I with List-II.
| List-I (Observation) | List-II (Reason) |
|---|---|
| (A) Sodium chloride dissolves readily in water but not in benzene. | (I) Solids and liquids are highly incompressible. |
| (B) The concentration of a saturated solution stays constant at a given temperature and pressure. | (II) The dissolution equilibrium follows Le Chatelier’s principle. |
| (C) Pressure has no significant effect on the solubility of a solid in a liquid. | (III) Polar solutes dissolve in polar solvents. |
| (D) The solubility of a solid whose dissolution is exothermic decreases with rise in temperature. | (IV) Dissolution and crystallisation take place at the same rate. |
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → A-III, B-IV, C-I, D-II
How much of a solid dissolves in a liquid depends on the nature of the solute and solvent and on temperature; pressure has almost no effect. In a saturated solution, the solid and the solution are in dynamic equilibrium:
\( \displaystyle \text{Solute} + \text{Solvent} \ce{<=>} \text{Solution} \)
(A) Sodium chloride dissolves readily in water but not in benzene. — This matches (III) Polar solutes dissolve in polar solvents. Sodium chloride and water are both polar, while benzene is non-polar: like dissolves like.
(B) The concentration of a saturated solution stays constant at a given temperature and pressure. — This matches (IV) Dissolution and crystallisation take place at the same rate. As many solute particles go into the solution as separate out, so the concentration does not change.
(C) Pressure has no significant effect on the solubility of a solid in a liquid. — This matches (I) Solids and liquids are highly incompressible. A change in pressure hardly changes them, so the solubility stays the same.
(D) The solubility of a solid whose dissolution is exothermic decreases with rise in temperature. — This matches (II) The dissolution equilibrium follows Le Chatelier’s principle. Heat is given out on dissolving, so heating shifts the equilibrium back and less solid stays dissolved.
NCERT (2026-27 edition):
1.3.1 Solubility of a Solid in a Liquid – “While sodium chloride and sugar dissolve readily in water, naphthalene and anthracene do not. On the other hand, naphthalene and anthracene dissolve readily in benzene but sodium chloride and sugar do not. It is observed that polar solutes dissolve in polar solvents and non polar solutes in non- polar solvents.”
“…A stage is reached when the two processes occur at the same rate. Under such conditions, number of solute particles going into solution will be equal to the solute particles separating out and a state of dynamic equilibrium is reached. … At this stage the concentration of solute in solution will remain constant under the given conditions, i.e., temperature and pressure.”
“…This, being dynamic equilibrium, must follow Le Chateliers Principle. In general, if in a nearly saturated solution, the dissolution process is endothermic (ΔsolH > 0), the solubility should increase with rise in temperature and if it is exothermic (ΔsolH < 0) the solubility should decrease.”
“Pressure does not have any significant effect on solubility of solids in liquids. It is so because solids and liquids are highly incompressible and practically remain unaffected by changes in pressure.”