Base (chemistry)

The common (Arrhenius) definition of a base, also known as an alkaline compound, is a chemical compound that either donates hydroxide ions or absorbs hydrogen ions when dissolved in water. Bases and acids are seen as opposites because the effect of an acid is to increase the hydronium ion (H3O) concentration in water, whereas bases reduce this concentration. Arrhenius bases are water-soluble and these solutions always have a pH greater than 7.

Common bases

• Baking soda (sodium hydrogen carbonate)
• Sodium carbonate
• Ammonia and amines
• Pyridine and other basic aromatic rings
• Metal hydroxides like sodium hydroxide or potassium hydroxide
• Many metal oxides form basic hydroxides with water (anhydrides)