Hypochlorite
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An hypochlorite is chemical compound containing the ClO− ion.
Contents
General properties
Hypochlorites are unstable compounds, and will disproportionate to chlorate and chloride:
- 3 NaClO → NaClO3 + 2 NaCl
This reaction is accelerated by heat.
Hypochlorite is the strongest oxidizing member of the chlorine oxyanions.
The alkali metal hypochlorites decrease in stability down the group. Anhydrous lithium hypochlorite is stable at room temperature in both solid and liquid form, while sodium hypochlorite has not be prepared drier than the pentahydrate (NaOCl·5 H2O), which itself is unstable above 0 °C, although it's much more stable in dilute solutions. Potassium hypochlorite (KOCl) is known only in solution.
Hypochlorous acid itself is not stable in isolation, as it decomposes to form chlorine.
Ammonium hypochlorite does not exist, as ammonia or ammonium compounds are immediately oxidized by the hypochlorite to chloramines.
Organic hypochlorites, such as methyl hypochlorite, are highly unstable, with the latter being explosive.
Availability
Hypochlorites are available in two main forms: the unstable sodium hypochlorite, sold as common household bleach and calcium hypochlorite, sold as impure bleaching powder.
The more stable lithium hypochlorite is sold by chemical suppliers, albeit it is more expensive.
Preparation
Hypochlorites can be obtained from the electrolysis of a chloride salt.
- 2 Cl− → Cl2 + 2 e−
- Cl2 + H2O ⇌ HClO + Cl− + H+
Bubbling chlorine gas in an alkaline solution will generate hypochlorite.
- 2 NaOH + Cl2 → NaClO + NaCl + H2O
Hypochlorous acid can be generated by adding an acid to bleach, though this route may also produce lots of chlorine gas.
Safety
Hypochlorites are highly corrosive and toxic.
NEVER MIX BLEACH WITH AMMONIA! It will generate very toxic chloramines!
Hypochlorites are best neutralized with a reducing agent, like sodium/potassium thiosulfate/sulfite/metabisulfite. Hydrogen peroxide can also be used, but the neutralization reaction will generate lots of oxygen.
