Ammonium hydroxide, also known as ammonia solution, is a weak base. It doesn't have a fixed pH value because its pH depends on its concentration.

Here's why:

* Equilibrium: Ammonium hydroxide (NH₄OH) exists in equilibrium with ammonia (NH₃) and water (H₂O). This equilibrium reaction determines the concentration of hydroxide ions (OH⁻), which directly affects the pH.

* Concentration: The higher the concentration of ammonium hydroxide, the more hydroxide ions are present, resulting in a higher pH (more basic).

* Variable pH: A dilute solution of ammonium hydroxide will have a pH closer to 7 (neutral), while a concentrated solution will have a pH higher than 7 (basic).

To determine the exact pH of a specific solution of ammonium hydroxide, you would need to know its concentration and use the appropriate equilibrium constant (Kb) for the reaction.

Here's a general idea of the pH range for ammonium hydroxide solutions:

* Dilute solutions: pH around 10-11

* Concentrated solutions: pH around 12-13

Remember that these are approximate values, and the actual pH can vary depending on the specific concentration of the solution.