Chloric acid

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Chloric acid
Chloric acid
Chloric acid
CAS number 7790-93-4
ChemSpider 18513
Jmol-3D images Image 1
Molecular formula HClO3
Molar mass 84.45914 g mol−1
Appearance colourless solution
Density 1 g/mL, solution (approximate)
Solubility in water >40 g/100 ml (20 °C)
Acidity (pKa) ca. −1
Molecular shape pyramidal
MSDS External MSDS
Main hazards Oxidant, Corrosive
Related compounds
Other anions bromic acid
iodic acid
Other cations ammonium chlorate
sodium chlorate
potassium chlorate
Related compounds hydrochloric acid
hypochlorous acid
chlorous acid
perchloric acid
Supplementary data page
Structure and
n, εr, etc.
Phase behaviour
Solid, liquid, gas
Spectral data UV, IR, NMR, MS
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
Infobox references

Chloric acid, HClO3, is an oxoacid of chlorine, and the formal precursor of chlorate salts. It is a strong acid (pKa ≈ −1) and oxidizing 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 also produced by the reaction of sulfuric acid with potassium chlorate in the combustion of sugar using potassium chlorate, sulfuric acid, and sugar.

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.

Chloric acid is a dangerously powerful oxidizing agent and will cause most organics and flammables to deflagrate on contact. For example a mixture of potassium chlorate and sugar will burn when concentrated sulfuric acid is added due to chloric acid production. Because sulfur tends to contain acidic impurities, it will form highly unstable mixtures with potassium chlorate due to chloric acid being produced.

See also[edit]