Question

Explain the following: Sodium chloride is an ionic compound which does not conduct electricity in solid state whereas it does conduct electricity in molten state as well as in aqueous solution.

Answer 1

Solid $\mathrm{NaCl}$ does not conduct electricity:-

• Although Sodium chloride $\mathrm{NaCl}$ is an ionic compound, it still does not conduct electricity in the solid-state.
• We know that flow of electrons is needed for the conduction of electricity.
• In the solid form of Sodium chloride, the particles are closely packed with each other due to the rigid structure, and hence they cannot move and are in a fixed position.
• As a result the flow of electrons is not possible and thus it does not conduct electricity.

Molten and aqueous $\mathrm{NaCl}$ conducts electricity:-

• In the molten and the aqueous form, Sodium chloride $\mathrm{NaCl}$ conducts electricity.
• This is because, in the molten or aqueous state, the flow of electrons is possible, as they are not held tightly or closely, to each other.
• Due to this factor, Sodium chloride dissociates into Sodium and Chloride ions and hence conduction of electricity is possible:

$\underset{\mathrm{Sodium}\mathrm{chloride}}{\mathrm{NaCl}\left(\mathrm{aq}\right)}\to \underset{\mathrm{Sodium}\mathrm{ions}}{{\mathrm{Na}}^{+}\left(\mathrm{aq}\right)}+\underset{\mathrm{Chloride}\mathrm{ions}}{{\mathrm{Cl}}^{-}\left(\mathrm{aq}\right)}$