Chloric acid
Names Other names Identifiers ChemSpider ECHA InfoCard 100.029.303 EC Number UNII UN number 2626 Properties HClO3 Molar mass 84.45914 g mol−1 Appearance colourless solution Density 1 g/mL, solution (approximate) >40 g/100 ml (20 °C) Acidity (pKa) −2.7[1] Conjugate base Chlorate Structure pyramidal Hazards Occupational safety and health (OHS/OSH): Oxidant, Corrosive GHS labelling: Danger H271, H314 P210, P220, P221, P260, P264, P280, P283, P301+P330+P331, P303+P361+P353, P304+P340, P305+P351+P338, P306+P360, P310, P321, P363, P370+P378, P371+P380+P375, P405, P501 NFPA 704 (fire diamond) Related compounds bromic acidiodic acid ammonium chloratesodium chloratepotassium chlorate hydrochloric acidhypochlorous acidchlorous acidperchloric acid
Chloric acid, HClO3, is an oxoacid of chlorine, and the formal precursor of chlorate salts. It is a strong acid (pKa ≈ −2.7) and an oxidizing agent.
Chloric acid is thermodynamically unstable with respect to disproportionation.
Chloric acid 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.[2] Above these concentrations, chloric acid solutions decompose to give a variety of products, for example:[2]
8 HClO3 → 4 HClO4 + 2 H2O + 2 Cl2 + 3 O2 3 HClO3 → HClO4 + H2O + 2 ClO2
When it reacts, it forms chlorate (ClO3) salts.
Chloric acid is a powerful oxidizing agent which ignites most organic materials on contact. It is also corrosive.[3]
Chloric acid may be produced from barium chlorate through its reaction with sulfuric acid, resulting in a solution of chloric acid and insoluble barium sulfate precipitate:[4]
Ba(ClO3)2 + H2SO4 → 2 HClO3 + BaSO4
The chlorate must be dissolved in boiling water and the acid should be somewhat diluted in water and heated before mixing.
Another method which can be used to produce solutions up to 10% concentration is by the use of cation exchange resins and a soluble salt such as NaClO3, where the Na+ cation will exchange with H+.[4]
Another method is the heating of hypochlorous acid, producing chloric acid and hydrogen chloride:[citation needed]
3 HClO → HClO3 + 2 HCl
Any way it is produced, the acid may be concentrated up to 40% in a vacuum dessicator over H2SO4.[4]
- Chlorate
- Hypochlorous acid
- Chlorous acid
- Perchloric acid
- Oxidizing acid
- Dichlorine pentoxide
- Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. doi:10.1016/C2009-0-30414-6. ISBN 978-0-08-037941-8.
- R. Bruce King, ed. (1994). “Chloric acid”. Encyclopedia of Inorganic Chemistry. Vol. 2. Chichester: Wiley. p. 658. ISBN 0-471-93620-0.