The equilibrium constant expression for the reaction of a weak acid HA dissociating in water is given by the acid dissociation constant Ka . The reaction can be represented as:HA aq H+ aq + A- aq The equilibrium constant expression for this reaction is:Ka = [H+][A-] / [HA]To determine the equilibrium constant Ka experimentally using pH measurements, follow these steps:1. Prepare a solution of the weak acid with a known concentration C in water.2. Measure the pH of the solution using a pH meter or pH indicator.3. Calculate the concentration of H+ ions [H+] in the solution using the pH value: [H+] = 10^-pH 4. Since the weak acid dissociates into H+ and A- ions, the concentration of A- ions [A-] will be equal to the concentration of H+ ions: [A-] = [H+]5. The initial concentration of the weak acid HA will decrease by the amount of H+ ions formed. Therefore, the equilibrium concentration of HA [HA] can be calculated as: [HA] = C - [H+]6. Substitute the values of [H+], [A-], and [HA] into the Ka expression and solve for Ka: Ka = [H+][A-] / [HA]By following these steps, you can experimentally determine the equilibrium constant Ka for the dissociation of a weak acid in water using pH measurements.