Question

Identify the following substance that is underlined: A Gas which does not conduct electricity in the liquid state but conducts electricity when dissolved in water.

Answer 1

Conductivity: A substance conduct electricity due to the presence of free electrons in the valence shell or due to the presence of free ions in an aqueous solution.

• A gas that does not conduct electricity in the liquid state but conducts electricity when dissolved in water is Hydrogen chloride gas.
• $\mathrm{HCl}$ in its gas phase does not conduct electricity, when it is dissolved in water it makes a solution of hydrochloric acid and dissociates into ions which are free to move and conducts electricity.
• The balanced chemical reaction of dissociation of hydrochloric acid can be represented as:

$\underset{\mathrm{Hydrochloric}\mathrm{acid}}{\mathrm{HCl}\left(\mathrm{aq}\right)}\to \underset{\mathrm{Hydrogen}\mathrm{ion}}{{\mathrm{H}}^{+}\left(\mathrm{aq}\right)}+\underset{\mathrm{Chloride}\mathrm{ion}}{{\mathrm{Cl}}^{-}\left(\mathrm{aq}\right)}$

• So, hydrogen chloride in a liquid state due to the presence of hydrogen and chloride ions.

Hence, Hydrogen chloride is a gas that does not conduct electricity in the liquid state but conducts electricity when dissolved in water.