Determine the acid dissociation constant for a 0.020 M formic acid solution that has a pH of 2.74.Formic acid is a weak monoprotic acid and the equilibrium equation of interest is HCOOH(aq)+ H₂O(l)⇌ H₃O⁺(aq)+ HCO₂^-(aq).

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The pH of the solution is 2.74, which means the concentration of H+ ions is 10^-2.74. For a weak acid like formic acid, the concentration of H+ ions is approximately equal to the concentration of its conjugate base, HCOO-, at equilibrium. The acid dissociation constant, Ka, is given by Ka = [H+][HCOO-]/[HCOOH]. Since [H+] = [HCOO-] = 10^-2.74 and the initial concentration of HCOOH is 0.020 M, assuming x (the dissociation) is small compared to the initial concentration, the concentration of HCOOH at equilibrium is approximately 0.020 M. Therefore, Ka ≈ (10^-2.74)^2 / 0.020 = 1.8 × 10^-4.

Determine the Acid Dissociation Constant for a 0