Chlorous acid
| Names | |
|---|---|
| IUPAC name
Chlorous acid
| |
| Other names
Hypochloric acid
Hydrogen dioxochlorate(III) | |
| Properties | |
| HClO2 | |
| Molar mass | 68.46 g/mol |
| Appearance | Colorless unstable liquid |
| Odor | Acrid |
| Miscible | |
| Solubility | Reacts with amines and alkali, hydrogen peroxide |
| Acidity (pKa) | 1.96 |
| Thermochemistry | |
| Std molar
entropy (S |
-319.4 J·K−1·mol−1 |
| Std enthalpy of
formation (ΔfH |
175.3 kJ/mol |
| Hazards | |
| Safety data sheet | None |
| Related compounds | |
| Related compounds
|
Hydrochloric acid Hypochlorous acid Chloric acid Perchloric acid |
| Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). | |
| Infobox references | |
Chlorous acid is an inorganic compound with the formula HClO2. It is a weak acid.
Chlorine is the only halogen to form an isolable acid of formula HXO2. Neither bromous acid nor iodous acid has ever been isolated. A few salts of bromous acid, bromites, are known, but no iodites.
Contents
Properties
Chemical
The pure acid is unstable, disproportionating to hypochlorous acid and chloric acid:
- 2 HClO2 → HClO + HClO3
Both resulting acids are also unstable in concentrated form, and will too further decompose to hydrochloric acid, perchloric acid chlorine, chlorine dioxide and oxygen.
Physical
Chlorous acid is an unstable clear liquid, with an acrid odor.
Availability
The compound is not sold and has to be made in situ.
Preparation
HClO2 can be prepared through reaction of barium or lead chlorite and dilute sulfuric acid:
- Ba(ClO2)2 + H2SO4 → BaSO4 + 2 HClO2
- Pb(ClO2)2 + H2SO4 → PbSO4 + 2 HClO2
Projects
- Make perchloric acid
Handling
Safety
Chlorous acid is an unstable but corrosive compound. Wear proper protection when handling it.
Storage
Cannot be stored, decomposes.
Disposal
Can be neutralized with a base containing a reducing agent, like thiosulfate, sulfite or metabisulfite.
