Special points about DIC, pH, and other weak acids When pH = pK a, concentration of protonated in reactant = deprotonated in product – pK a = -log K a – for H 2 CO 3 ↔ HCO 3 - + H +, K a = 10 -6.35, pK a = 6.35 – so for H 4 SiO 4 ↔ H 3 SiO 4 - + H +, pK a = 9.71 – And for H 3 SiO 4 -  H + + H 2 SiO 4 2-, pK a = 13.28 19
{}