Final answer:
The dissociation of the weak acid trichloroacetic acid (HC₂Cl₃O₂) in water is an equilibrium reaction, resulting in the production of hydronium ions (H₃O+) and trichloroacetate ions (C₂Cl₃O₂⁻). The acid dissociation constant, Ka, for this reaction is written as the product of the concentrations of the hydronium and trichloroacetate ions divided by the concentration of the undissociated acid.
Step-by-step explanation:
The dissociation of a weak acid, such as trichloroacetic acid (HC₂Cl₃O₂), in water can be represented by an equilibrium reaction and a corresponding acid dissociation constant (Ka) expression. Trichloroacetic acid is structurally similar to pyruvic acid, but instead of the pyruvate ion, we obtain the trichloroacetate ion upon dissociation in water. The reaction is as follows:
HC₂Cl₃O₂(aq) + H₂O(l) ⇌ H₃O+(aq) + C₂Cl₃O₂⁻(aq)
The Ka expression for this dissociation is:
Ka = [H₃O+][C₂Cl₃O₂⁻] / [HC₂Cl₃O₂]
Ka values are a measure of the extent of dissociation of weak acids. A smaller Ka value indicates a weaker acid, meaning the dissociation is less complete and the acid donates fewer protons to the water.