Final answer:
A base yields hydroxide ions when dissolved in water. Ammonia is a base that, upon dissolving in water, reacts to form ammonium ions and hydroxide ions, slightly increasing the hydroxide ion concentration in the solution.
Step-by-step explanation:
A base is a substance that yields hydroxide ions (OH⁻) when dissolved in water. Ammonia (NH₃) is also a base because when it is put into water, it reacts with the water to form ammonium ions (NH₄⁺) and hydroxide ions (OH⁻). This reaction can be represented by the following chemical equation:
NH₃(aq) + H₂O(l) ⇒ NH₄⁺(aq) + OH⁻(aq)
Although ammonia is a weak base, it nonetheless increases the concentration of hydroxide ions in the solution, albeit not as much as a strong base would. Weak bases in household use, alongside ammonia, include substances such as sodium hypochlorite (NaClO) in bleach, sodium carbonate (Na₂CO₃) and trisodium phosphate (Na3PO4) in laundry detergents, sodium bicarbonate (NaHCO₃) in toothpaste and baking powder, calcium carbonate (CaCO₃) for use on lawns, and magnesium hydroxide (Mg(OH)₂) and aluminum hydroxide (Al(OH)₃) in antacids and laxatives.