Dissociation of alkalis

In contrast, an alkali dissociates to release OH^- ions. These OH^- ions bind to any free H⁺ ions already in the solution (forming water or H₂O). This causes the number of free H⁺ ions to drop and the pH value to increase. Alkalis are therefore sometimes also known as H⁺ ion acceptors.

A weak alkali is CHNaO₃ – also known as baking soda or bicarbonate of soda. When it dissociates in water it does not release many of its OH^- ions. By contrast, a strong alkali like NaOH (sodium hydroxide or caustic soda) releases almost all of its OH^- ions in solution.

Alkaline solutions have a large number of free OH^- ions in solution. These OH^- ions like to bind to any free H⁺ ions. This makes the pH number or value of an alkaline solution large, since pH measures the number of free H⁺ ions.