Question

Potassium chloride is an electrovalent compound, while hydrogen chloride is a covalent compound. Both conduct electricity in their aqueous solutions. Explain.

Answer 1

Reason for the conductance of electricity:

The movement of free ions is responsible for the conduction of electricity.

Potassium chloride (KCl):

Potassium chloride is an electrovalent compound formed by the transfer of electrons from Potassium (K) to Chlorine (Cl).

• Electrovalent compounds are made up of ions that are held together by strong electrostatic forces of attraction.
• These forces of attraction are overcome by the water due to its polar nature.
• Hence, dissociation of ions occurs in the aqueous solution as shown below:
• $$\begin{gathered} \mathrm{KCl}\rightleftharpoons {\mathrm{K}}^{+}+{\mathrm{Cl}}^{-} \\ (\mathrm{Potassium}(\mathrm{Potassium}\mathrm{ion})(\mathrm{Chloride}\mathrm{ion}\left) \\ \mathrm{chloride}\right) \end{gathered}$$

The ions already present in Potassium chloride become free due to which they conduct electricity.

Hydrogen chloride (HCl):

Hydrogen chloride is a molecular compound that does not have ions. It is a covalent compound formed by the mutual sharing of electrons between Hydrogen and Chlorine.

• But on dissolution in water, it reacts with water to furnish ions as shown below.
• $$\begin{gathered} \mathrm{HCl}+{\mathrm{H}}_2\mathrm{O}\rightleftharpoons {\mathrm{H}}_3{\mathrm{O}}^{+}+{\mathrm{Cl}}^{-} \\ (\mathrm{Hydrogen}\mathrm{chloride})\left(\mathrm{Water}\right)(\mathrm{Hydronium}\mathrm{ions})(\mathrm{Chloride}\mathrm{ions}) \end{gathered}$$

As ions are made available in an aqueous solution, therefore even Hydrogen chloride conducts electricity in the water.