Calcium peroxide

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Calcium peroxide

Template:Longitem	Template:Unbulleted list
ChEBI	Template:Unbulleted list
ChemSpider	Template:Unbulleted list
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EC Number	Template:Unbulleted list
Template:Longitem	674257
KEGG	Template:Unbulleted list
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RTECS number	Template:Unbulleted list
UN number	1457
Template:Longitem	Template:Chembox Elements/molecular formula
Molar mass	Template:Chem molar mass
Appearance	white or yellowish powder
Odor	odorless
Density	2.91 g/cm3
Melting point	Template:Chembox CalcTemperatures
Acidity (pKa)	12.5
Template:Longitem	−23.8·10−6 cm3/mol
Template:Longitem	1.895
Template:Longitem	Orthorhombic
Template:Longitem	Pna21
Template:Longitem	8
Template:Longitem	Calcium oxide
Template:Longitem	Strontium peroxide Barium peroxide Sodium peroxide

Calcium peroxide or calcium dioxide is the inorganic compound with the formula CaO₂. It is the peroxide (O₂²⁻) salt of Ca²⁺. Commercial samples can be yellowish, but the pure compound is white. It is almost insoluble in water.

Structure and stability

As a solid, it is relatively stable against decomposition. In contact with water however it hydrolyzes with release of oxygen. Upon treatment with an acid, it forms hydrogen peroxide.

$2\mathrm{C}\mathrm{a}\mathrm{O}{\phantom{A}}_2+2\mathrm{H}{\phantom{A}}_2\mathrm{O}⟶2\mathrm{C}\mathrm{a}(\mathrm{O}\mathrm{H}){\phantom{A}}_2+\mathrm{O}{\phantom{A}}_2$

$\mathrm{C}\mathrm{a}\mathrm{O}{\phantom{A}}_2+2\mathrm{H}{\phantom{A}}^{+}⟶\mathrm{C}\mathrm{a}{\phantom{A}}^{2+}+\mathrm{H}{\phantom{A}}_2\mathrm{O}{\phantom{A}}_2$

Preparation

Calcium peroxide is produced by combining calcium salts and hydrogen peroxide:

Ca(OH)₂ + H₂O₂ → CaO₂ + 2 H₂O

The octahydrate precipitates upon the reaction of calcium hydroxide with dilute hydrogen peroxide. Upon heating it dehydrates.

Applications

It is mainly used as an oxidant to enhance the extraction of precious metals from their ores. In its second main application, it is used as a food additive under the E number E930 it is used as flour bleaching agent and improving agent.

In agriculture it is used in the presowing treatments of rice seed. Also, calcium peroxide has found use in aquaculture to oxygenate and disinfect water. In the ecological restoration industry it is used in the treatment of soils. Calcium peroxide is used in a similar manner to magnesium peroxide for environmental restoration programs. It is used to restore soil and groundwater contaminated with petroleum by the process of enhanced in-situ bioremediation. It is a minor component of some dentifrices.

It is also used for curing Template:Chem name polymers by oxidising terminal thiol groups to disulphide bridges.