Question

Why does an aqueous solution of acid conduct electricity?

Answer 1

Hint: We should know that for the conduction of electricity, ions are necessary things.
Now try to figure out the reason for the conduction of electricity by an aqueous solution of acid.

Complete step by step answer:
You must be aware that pure acids in the liquid state are exceedingly poor conductors of electricity. The fact that aqueous solutions of acids conduct electricity is definite evidence of the existence of ions in these solutions.
Acids undergo dissociation in aqueous solution to form $H^{ + }$ ions. When electricity is passed through an aqueous solution of an acid, the $H^{ + }$ ions reach the cathode, and each $H^{ + }$ ion picks up one electron from the cathode to form $H_{ 2 }$ gas.
So, we can say, an aqueous solution of acid conducts electricity due to this reaction
$HCl(aq)\quad \rightarrow \quad H^{ + }(aq)\quad +\quad Cl^{ - }(aq)$
Therefore, we can conclude it as an aqueous solution of an acid that conducts electricity because, in water, an acid (HCl) dissociates to give ions. Since the current is carried out by the movement of ions, an aqueous solution of acid conducts electricity.

Note: We should also know that during dilution, more acid dissociates into ions. Thus, the concentration of $[H_{ 3 }O]^{ + }$ ions will increase on dilution. Even on increasing $[H_{ 3 }O]^{ + }$ ions, the number of ions per unit volume decreases. Therefore, pH will increase on dilution.