Final answer:
The interaction of a weak base with water is represented by the equation B(aq) + H₂O(l) ⇒ BH+(aq) + OH⁻(aq), where the weak base forms its conjugate acid and a small proportion of hydroxide ions. An example of this is the reaction of trimethylamine with water, which does not fully dissociate and reaches equilibrium mostly in the nonionized base form.
Step-by-step explanation:
The equation that represents the interaction of a weak base with water is B(aq) + H₂O(l) ⇒ BH+(aq) + OH⁻(aq). This equation shows that when a weak base (represented by B) reacts with water, it forms its conjugate acid (BH+) and hydroxide ions (OH⁻), though not to the extent that a strong base would. The reaction of water acting as an acid with the weak base forms these two products. A weak base will give only a small proportion of hydroxide ions compared to a strong base, which fully dissociates in water.
For example, a weak base such as trimethylamine ((CH3)3N), interacts with water as follows: (CH3)3N(aq) + H₂O(l) ⇒ (CH3)3NH+(aq) + OH⁻(aq). This reaction reaches an equilibrium where most of the base is in the nonionized form.
Overall, the strength of a base is determined by its tendency to form hydroxide ions when dissolved in water. The equilibrium constant for the ionization of a weak base, known as the base ionization constant (Kb), helps in quantitating this tendency. A base that has a Kb value closer to that of water is a weaker base, whereas one with a Kb value further from that of water is a stronger base.