​The solubility of NaCl is greater in water than ethanol. What physical property of the solvent governs this difference?

Correct option is C

Explanation:

• Solubility of NaCl (an ionic compound) depends on the ability of the solvent to dissociate its ions (Na⁺ and Cl⁻) and stabilize them.
• Water has a much higher dielectric constant (~78.5) than ethanol (~24.3), making it a better polar solvent for dissolving ionic compounds like NaCl.
• The dielectric constant of a solvent measures its ability to reduce the electrostatic forces between charged particles. A higher dielectric constant means better ion solvation.
• Since ethanol has a lower dielectric constant, it is less effective in breaking the strong ionic bonds in NaCl, leading to lower solubility.
• This explains why NaCl dissolves much more in water than in ethanol.

Information Booster

1. Dielectric constant (εr) is a measure of a solvent's ability to reduce the electrostatic attraction between ions.
2. Higher dielectric constant = better solvation of ionic compounds, as it weakens ion-ion interactions.
3. Water (εr ≈ 78.5 at 25°C) dissolves salts well, while ethanol (εr ≈ 24.3) is less effective.
4. Ethanol has both polar (-OH) and non-polar (-C₂H₅) parts, making it less effective for dissolving salts.
5. Other solvents with high dielectric constants include methanol (εr ≈ 32.6) and formamide (εr ≈ 109).
6. Non-polar solvents like hexane (εr ≈ 1.9) cannot dissolve ionic compounds because they lack strong dipole interactions.

Additional Information

• Option (a) Surface tension: Surface tension is related to intermolecular forces but does not directly affect ionic solubility.
• Option (b) Viscosity: Viscosity affects the flow of liquids but has no significant impact on salt solubility.
• Option (d) Boiling point: Boiling point is a property related to intermolecular forces, but it does not determine ionic solubility.