Arrheniuselmélet

Arrhenius theory, also known as the Arrhenius definition of acids and bases, is a fundamental concept in chemistry that describes the behavior of acids and bases in aqueous solutions. Proposed by Swedish chemist Svante Arrhenius in 1884, this theory provides a simple yet powerful framework for understanding acid-base reactions.

According to the Arrhenius theory, an acid is a substance that increases the concentration of hydrogen ions (H+) when dissolved in water. These hydrogen ions are often represented as hydronium ions (H3O+) when they combine with water molecules. For example, hydrochloric acid (HCl) dissociates in water to produce H+ and Cl- ions.

Conversely, a base is defined as a substance that increases the concentration of hydroxide ions (OH-) when dissolved in water. A classic example is sodium hydroxide (NaOH), which dissociates in water to form Na+ and OH- ions.

The Arrhenius theory is particularly useful for explaining neutralization reactions, where an acid and a base react to form salt and water. In this process, the H+ ions from the acid combine with the OH- ions from the base to form water. The remaining ions from the acid and base form the salt.

While the Arrhenius theory has been highly influential and remains a useful model for many common acids and bases, it has limitations. It is primarily applicable to aqueous solutions and does not adequately explain the behavior of substances that act as acids or bases in non-aqueous solvents or in the gas phase. Furthermore, it does not account for species like ammonia (NH3), which acts as a base but does not contain hydroxide ions in its formula. Despite these limitations, the Arrhenius theory laid the groundwork for more comprehensive acid-base theories, such as the Brønsted-Lowry and Lewis theories.