1. Ammonia as a Weak Base:
* Ammonia is a weak base, meaning it doesn't completely ionize in water. Instead, it establishes an equilibrium with its conjugate acid, the ammonium ion (NH4+):
NH3(aq) + H2O(l) ⇌ NH4+(aq) + OH-(aq)
* The equilibrium lies to the left, meaning that most of the ammonia remains in its molecular form.
2. Hydroxide Ion Formation:
* The reaction between ammonia and water produces a small amount of hydroxide ions (OH-) and ammonium ions (NH4+).
* The presence of OH- ions is what makes the solution basic.
3. Equilibrium Shift:
* While ammonia is a weak base, it still has the ability to accept protons (H+) from water molecules.
* As the ammonia molecules react with water, they shift the equilibrium to the right, increasing the concentration of hydroxide ions.
In Summary:
Ammonia raises the hydroxide ion concentration by reacting with water to form a small amount of hydroxide ions and ammonium ions. Although the equilibrium favors the reactants, the presence of even a small amount of hydroxide ions makes the solution basic.
