When hydrochloric acid (HCl) is mixed with water, it dissociates into its constituent ions. This process releases heat and results in a highly acidic solution. The equation for this reaction can be represented as follows:
\[ \text{HCl (aq)} \rightarrow \text{H}^+ (aq) + \text{Cl}^- (aq) \]
In this reaction:
- HCl is the strong acid that fully dissociates in water.
- H⁺ ions are produced, which are responsible for the acidic properties of the solution.
- Cl⁻ ions are the chloride ions.
Because HCl is a strong acid, it ionizes completely in water, which means that even a small concentration of HCl will significantly increase the hydrogen ion concentration in the solution, resulting in a low pH.
Additionally, the mixing of HCl with water is exothermic, meaning it releases heat. Therefore, it is generally advised to add acid to water and not the other way around to avoid splashing and exothermic reactions that could lead to dangerous situations.