NaOH (sodium hydroxide) is considered a strong alkali because of its ability to completely dissociate in water, releasing a high concentration of hydroxide ions (OH⁻). Here's a breakdown:

* Dissociation: When NaOH dissolves in water, it breaks apart into its constituent ions: Na⁺ (sodium ion) and OH⁻ (hydroxide ion).

* Complete Dissociation: Unlike weak alkalis, which only partially dissociate, NaOH undergoes complete dissociation. This means that essentially all of the NaOH molecules break apart into ions, generating a high concentration of OH⁻.

* High Concentration of OH⁻: The high concentration of OH⁻ ions is what makes NaOH a strong alkali. Hydroxide ions are responsible for the basic properties of solutions.

In summary: The strong alkali nature of NaOH is due to its complete dissociation in water, leading to a high concentration of hydroxide ions (OH⁻). This high concentration of OH⁻ makes solutions containing NaOH very basic.