Hypochlorous acid is a weak acid, as indicated by the extremely small ionization (Ka) value. As such, when the acid is an aqueous environment, the following equilibrium reaction will occur: HClO + H2O <---> H3O+ + ClO- Create an ICE table, which is a useful organization tool in equilibrium chemistry. HClO + H2O <---> H3O+ + ClO- I 0.0684 0 0 C -x +x +x E 0.0684 x x I stands for initial concentrations; C for change; and E for equilibrium concentrations. The reason why E for HClO is the same as I is because the dissociation constant is much smaller than the initial concentration, which means assuming the HClO concentration did not change is acceptable. Ionization constant = [H3O+][ClO-] / [HClO] [H3O+] = sqrt(3.5e-8 x 0.0684) pH = -log[H3O+] = 4.31

Are you asking for the pKa value?