Chloric acid

Chloric acid, HClO3, is an oxoacid of chlorine, and the formal precursor of chlorate salts. It is a strong acid (pKa ≈ −1) and oxidising agent.

It is prepared by the reaction of sulfuric acid with barium chlorate, the insoluble barium sulfate being removed by precipitation:
 * Ba(ClO3)2 + H2SO4 → 2HClO3 + BaSO4

Another method is the heating of hypochlorous acid, of which productions include chloric acid and hydrogen chloride:
 * 3HClO → HClO3 + 2 HCl

It is stable in cold aqueous solution up to a concentration of approximately 30%, and solution of up to 40% can be prepared by careful evaporation under reduced pressure. Above these concentrations, and on warming, chloric acid solutions decompose to give a variety of products, for example:
 * 8HClO3 → 4HClO4 + 2H2O + 2Cl2 + 3 O2
 * 3HClO3 → HClO4 + H2O + 2 ClO2

The decomposition is controlled by kinetic factors: indeed, chloric acid is never thermodynamically stable with respect to disproportionation.