* An acid: A substance that produces hydrogen ions (H+) when dissolved in water.
* A base: A substance that produces hydroxide ions (OH-) when dissolved in water.
The reaction:
When an acid and a base are mixed in water, they react to form salt and water.
The chemical equation:
```
Acid + Base → Salt + Water
```
Example:
The reaction between hydrochloric acid (HCl) and sodium hydroxide (NaOH):
```
HCl(aq) + NaOH(aq) → NaCl(aq) + H2O(l)
```
Explanation:
* HCl is an acid because it releases H+ ions in water.
* NaOH is a base because it releases OH- ions in water.
* The H+ ions from the acid combine with the OH- ions from the base to form water (H2O).
* The remaining ions (Na+ and Cl-) form the salt, sodium chloride (NaCl).
Key points:
* Arrhenius theory focuses on the formation of H+ and OH- ions in water.
* This definition is limited to reactions in aqueous solutions.
* The theory doesn't explain reactions in non-aqueous solvents or reactions without H+ or OH- ion formation.
The Arrhenius theory is a foundational concept in understanding acid-base chemistry, but it has limitations. More comprehensive theories like the Brønsted-Lowry and Lewis theories provide broader definitions of acids and bases.
