Chemistry of Acids
An examination of the chemistry of acids and bases reveals what happens when the two are combined. Acids are substances that generate positively charged ions when dissolved in aqueous (water-based solvent) solution. For instance, when hydrogen chloride (HCl) is dissolved in water, hydronium ions (H3O+) are released and hydrochloric acid is formed. These positively charged ions have a strong affinity for (are greatly attracted to) negatively charged ions.
Chemistry of Bases
Bases are substances that generate negatively charged ions when dissolved in aqueous solution. When sodium hydroxide (NaOH) is dissolved in water, hydroxide ions (OH―) are released. The negatively charged hydroxide ions have a strong affinity for positively charged ions. It is important to note that in both acidic and basic solutions, water is serving only as a solvent and does not undergo any chemical change.
The Acid-Base Reaction
When acids combine with bases, a chemical reaction does occur, resulting in products very much different from the original reactants. When hydrochloric acid (HCl) is combined with sodium hydroxide (NaOH), the hydronium ions (H3O+) combine with the hydroxide ions (OH―) to form water (H2O). The remaining chloride ions (Cl―) from the hydrochloric acid and the remaining sodium ions (Na+) from the sodium hydroxide combine to form sodium chloride (NaCl), common table salt. This reaction can be summarized by the following chemical equation:
A similar reaction occurs if different acids and bases are used. If the combining acid and base are equal in strength, the resulting salt solution is neither acidic nor basic. Because this often occurs, acid-base reactions are often neutralization reactions.