1. Ammonia is a Weak Base:

* Ammonia (NH₃) is a weak base. This means it only partially ionizes (dissociates) in water, releasing a small amount of hydroxide ions (OH⁻).

* The chemical equation for this reaction is:

NH₃(aq) + H₂O(l) ⇌ NH₄⁺(aq) + OH⁻(aq)

2. Hydroxide Ions Increase pH:

* The hydroxide ions (OH⁻) are responsible for the solution's alkalinity (basic nature). The higher the concentration of OH⁻ ions, the higher the pH value.

3. Equilibrium and Limited Ionization:

* While ammonia does react with water, the reaction is reversible. This means it reaches an equilibrium where some ammonia remains undissociated, and some is converted to ammonium ions (NH₄⁺) and hydroxide ions (OH⁻).

* Since ammonia is a weak base, the equilibrium favors the undissociated form of ammonia. This means the concentration of OH⁻ ions is relatively low compared to a strong base, but still high enough to significantly raise the pH.

In summary:

* Ammonia is a weak base, meaning it only partially ionizes in water, releasing a limited amount of hydroxide ions (OH⁻).

* The presence of these hydroxide ions increases the pH of the solution, making it basic.

* The higher the concentration of ammonia, the higher the concentration of OH⁻ ions, and the higher the pH value.