Hypochlorous acid
| Names | |
|---|---|
| IUPAC name
Hypochlorous acid
| |
| Other names
Chloranol
Chlorine hydroxide Hydrogen hypochlorite Hydroxidochlorine | |
| Properties | |
| HClO | |
| Molar mass | 52.46 g/mol |
| Appearance | Unstable colorless liquid (solution) |
| Odor | Strong chlorine odor |
| Melting point | Decomposes |
| Boiling point | Decomposes |
| Soluble | |
| Solubility | Reacts with bases |
| Acidity (pKa) | 7.53 |
| Hazards | |
| Safety data sheet | None |
| Flash point | Non-flammable |
| Related compounds | |
| Related compounds
|
Hydrochloric acid Chlorous 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 | |
Hypochlorous acid (HClO) is a weak acid that forms when chlorine dissolves in water, and itself partially dissociates, forming the hypochlorite anion ClO−.
Contents
Properties
Chemical
Hypochlorous acid is extremely unstable and rapidly decomposes, releasing oxygen gas:
- 2 HOCl → 2 HCl + O2
The reaction is catalyzed by light and metallic impurities.
HClO reacts with HCl to form chlorine gas:
- HClO + HCl → H2O + Cl2
HClO reacts with ammonia and amines form chloramines and water.
- NH3 + HClO → NH2Cl + H2O
HClO is a stronger oxidant than chlorine under standard conditions.
- 2 HClO(aq) + 2 H+ + 2 e- ⇌ Cl2(g) + 2 H2O E = +1.63 V
Physical
Hypochlorous acid only exists as solution, and thus its properties are derived from the solution.
Availability
Hypochlorous acid is not sold by anybody because it's too unstable to be of any use.
Preparation
Addition of chlorine to water gives both hydrochloric acid and hypochlorous acid:
- Cl2 + H2O ⇌ HClO + HCl
- Cl2 + 4 OH− ⇌ 2 ClO− + 2 H2O + 2 e−
- Cl2 + 2 e− ⇌ 2 Cl−
When acids are added to aqueous salts of hypochlorous acid (such as sodium hypochlorite in commercial bleach solution), the resultant reaction is driven to the left, and chlorine gas is formed. Thus, the formation of stable hypochlorite bleaches is facilitated by dissolving chlorine gas into basic water solutions, such as sodium hydroxide.
The acid can also be prepared by dissolving dichlorine monoxide in water; under standard aqueous conditions, anhydrous hypochlorous acid is currently impossible to prepare due to the readily reversible equilibrium between it and its anhydride:
- 2 HOCl ⇌ Cl2O + H2O
Projects
- Desinfectant
- Dissolve gold
- Make chlorohydrins
- Make ethylene oxide and propylene oxide
Handling
Safety
Hypochlorous acid is a powerful oxidizer and is highly corrosive.
Storage
Hypochlorous acid decomposes rapidly and cannot be stored. Hypochlorite salts are more stable, and can be kept as precursor for the acid when needed.
Disposal
Sodium thiosulfate can be used as neutralizing agent.
