Polyprotic Acids / pH Calculation
Home > Weak Acids and Bases – Calculate the pH of a weak acid (a general equation) > Solving Weak Acid and Weak Base pH problems > Weak Acid Weak Base pH calculation solved example > Weak Acid Weak Base pH calculation solved example > Cubic Equation Calculator for Weak Acid-Base Equilibria > Polyprotic Acids / pH Calculation Polyprotic Acids / pH Calculation A large number of acids can give two or more protons on ionization ( dissociation ) and these are referred to as polyprotic acids . For example, with sulfurous acid (H 2 SO 3 ) we have the successive ionizations: Fig. I.1: Stepwise dissociation of sulphurous acid (H 2 SO 3 ) A polyprotic acid always dissociates in a stepwise manner, one proton at a time. Note that the acid dissociation constants are labelled k a1 and k a2 . The numbers on the constants refer to the particular proton of the acid that is ionizing. Thus, k a1 always refers to the equilibrium involving removal of the first prot...