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.