Chromium(VI) peroxide
Encyclopedia
Chromium peroxide (CrO5) or chromium oxide peroxide is an unstable compound formed by the addition of acidified hydrogen peroxide
solutions to solutions of chromate
s, such as sodium chromate
. The generally yellow chromates turn to dark blue-brown as chromium(VI) peroxide is formed. The metal chromate reacts with hydrogen peroxide and an acid to give chromium peroxide, water, and the metal salt of the acid.
After a few seconds, they decompose to turn green as chromium(III) compounds are formed.
To avoid this decomposition, it is possible to stabilize chromium(VI) oxide peroxide in diethyl ether by adding a layer of ether above the (bi)chromate solution and shaking during the addition of hydrogen peroxide, so that the chromium(VI) peroxide (unstable in the aqueous phase in which newly formed) is dissolved in ether. In this condition it can be observed over a much longer period.
This compound contains one oxo ligand and two peroxo ligands, making a total of five oxygen atoms per chromium atom.
Hydrogen peroxide
Hydrogen peroxide is the simplest peroxide and an oxidizer. Hydrogen peroxide is a clear liquid, slightly more viscous than water. In dilute solution, it appears colorless. With its oxidizing properties, hydrogen peroxide is often used as a bleach or cleaning agent...
solutions to solutions of chromate
Chromate
Chromate salts contain the chromate anion, CrO42−. Dichromate salts contain the dichromate anion, Cr2O72−. They are oxyanions of chromium in the oxidation state +6. They are moderately strong oxidizing agents.- Chemical properties :...
s, such as sodium chromate
Sodium chromate
Sodium chromate is a yellow solid chemical compound used as a corrosion inhibitor in the petroleum industry, a dyeing auxiliary in the textile industry, as a wood preservative, and as a diagnostic pharmaceutical in determining red blood cell volume....
. The generally yellow chromates turn to dark blue-brown as chromium(VI) peroxide is formed. The metal chromate reacts with hydrogen peroxide and an acid to give chromium peroxide, water, and the metal salt of the acid.
- M2CrO4 + 2 H2O2 + 2 H+ → CrO5 + 3 H2O + 2 M+
After a few seconds, they decompose to turn green as chromium(III) compounds are formed.
To avoid this decomposition, it is possible to stabilize chromium(VI) oxide peroxide in diethyl ether by adding a layer of ether above the (bi)chromate solution and shaking during the addition of hydrogen peroxide, so that the chromium(VI) peroxide (unstable in the aqueous phase in which newly formed) is dissolved in ether. In this condition it can be observed over a much longer period.
- 2 CrO5 + 7 H2O2 + 6 H+ → 2 Cr3+ + 10 H2O + 7 O2
This compound contains one oxo ligand and two peroxo ligands, making a total of five oxygen atoms per chromium atom.