Before revision: Acidity Pyrophosphoric acid is a tetraprotic acid, with four distinct pKa's: , pKa = 0.85 , pKa = 1.96 , pKa = 6.60 , pKa = 9.41 The pKa's occur in two distinct ranges because deprotonations occur on separate phosphate groups.
After revision: Acidity Pyrophosphoric acid is a tetraprotic acid, with four distinct pKa1's: , pKa2 = 0.85 , pKa3 = 1.96 , pKa4 = 6.60 , pKa = 9.41 The pKa's occur in two distinct ranges because deprotonations occur on separate phosphate groups.