The ionization of acetic acid CHCOOH in water can be represented by the following chemical equation:CHCOOH aq + HO l CHCOO aq + HO aq In this reaction, acetic acid CHCOOH donates a proton H to water HO , forming the acetate ion CHCOO and the hydronium ion HO .The equilibrium constant expression for this reaction, known as the acid dissociation constant Ka , can be written as:Ka = [CHCOO][HO] / [CHCOOH]Here, [CHCOO] represents the equilibrium concentration of the acetate ion, [HO] represents the equilibrium concentration of the hydronium ion, and [CHCOOH] represents the equilibrium concentration of acetic acid.At 25C, the value of the equilibrium constant Ka for the ionization of acetic acid is approximately 1.8 x 10. This value indicates that the ionization of acetic acid in water is relatively weak, as the equilibrium lies towards the reactants undissociated acetic acid rather than the products acetate and hydronium ions .