The exact ionic equation for the neutralization reaction between hydrochloric acid (HCl) and potassium hydroxide (KOH) is K⁺(aq) + OH⁻(aq) + H⁺(aq) + Cl⁻(aq) = H₂O(l) + K⁺(aq) + Cl⁻(aq).
Neutralization reactions involve an acid and a base reacting to form water and a salt. While the molecular equation shows the complete neutral compounds, the ionic equation provides a clearer picture of the species (ions) that are actually present and participating in the reaction when dissolved in water.
Understanding the Ionic Equation
In the neutralization of hydrochloric acid (HCl) and potassium hydroxide (KOH), both reactants are strong electrolytes. This means they dissociate almost completely into ions when dissolved in water.
- Hydrochloric Acid (HCl): Being a strong acid, HCl dissociates into hydrogen ions (H⁺) and chloride ions (Cl⁻).
HCl(aq) → H⁺(aq) + Cl⁻(aq) - Potassium Hydroxide (KOH): As a strong base, KOH dissociates into potassium ions (K⁺) and hydroxide ions (OH⁻).
KOH(aq) → K⁺(aq) + OH⁻(aq) - Potassium Chloride (KCl): The salt formed, potassium chloride, is a soluble ionic compound and exists as separate ions in solution.
KCl(aq) → K⁺(aq) + Cl⁻(aq) - Water (H₂O): Water is a molecular compound and remains as molecules in this reaction.
Putting these dissociated species together gives the full ionic equation.
The Equation Components
The reference explicitly provides the ionic equation:
K⁺(aq) + OH⁻(aq) + H⁺(aq) + Cl⁻(aq) = H₂O(l) + K⁺(aq) + Cl⁻(aq)
Let's break down the components:
| Side | Reactants | Products |
|---|---|---|
| Left | K⁺(aq) (Potassium ion from KOH) | H₂O(l) (Water) |
| (Before) | OH⁻(aq) (Hydroxide ion from KOH) | K⁺(aq) (Potassium ion - remains dissolved) |
| H⁺(aq) (Hydrogen ion from HCl) | Cl⁻(aq) (Chloride ion - remains dissolved) | |
| Cl⁻(aq) (Chloride ion from HCl) |
This equation shows all the ions present in solution before and after the reaction, along with the formation of water. The ions that appear unchanged on both sides (K⁺ and Cl⁻) are called spectator ions because they do not directly participate in the formation of water. The core reaction that is happening is the combination of hydrogen ions and hydroxide ions to form water.
For comparison, the molecular equation for this reaction is:
KOH(aq) + HCl(aq) → H₂O(l) + KCl(aq)
The ionic equation clarifies which species are interacting at the ionic level in the aqueous solution.
