Iodine pentoxide

Iodine pentoxide is the chemical compound with the formula I2O5. This iodine oxide is the anhydride of iodic acid, and the only stable oxide of iodine. It is produced by dehydrating iodic acid at 200 °C in a stream of dry air:[1]

2HIO3 → I2O5 + H2O
Iodine pentoxide
Names
IUPAC name
Iodine pentoxide
Other names
Iodine(V) oxide
Iodic anhydride
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
ECHA InfoCard 100.031.569
UNII
  • InChI=1S/I2O5/c3-1(4)7-2(5)6 checkY
    Key: BIZCJSDBWZTASZ-UHFFFAOYSA-N checkY
  • InChI=1/I2O5/c3-1(4)7-2(5)6
    Key: BIZCJSDBWZTASZ-UHFFFAOYAR
  • O=I(=O)OI(=O)=O
Properties
I
2O
5
Molar mass 333.81 g/mol
Appearance white crystalline solid[1]
hygroscopic
Density 4.980 g/cm3[1]
Melting point 300 °C (572 °F; 573 K)[2] (decomposes)
Solubility soluble in water and nitric acid;
insoluble in ethanol, ether and CS2
−79.4·10−6 cm3/mol
Thermochemistry
-173.0 kJ/mol
Hazards
Occupational safety and health (OHS/OSH):
Main hazards
 oxidizer
NFPA 704 (fire diamond)
NFPA 704 four-colored diamond
3
0
0
OX
Related compounds
Other anions
 iodine pentafluoride
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
☒N verify (what is checkY☒N ?)
Infobox references
Iodine pentoxide
Fresh iodine pentoxide

Structure

I2O5 is bent with an I–O–I angle of 139.2°, but the molecule has no mirror plane so its symmetry is C2 rather than C2v. The terminal I–O distances are around 1.80 Å and the bridging I–O distances are around 1.95 Å.[3]

Reactions

Iodine pentoxide easily oxidises carbon monoxide to carbon dioxide at room temperature:

5 CO + I2O5 → I2 + 5 CO2

This reaction can be used to analyze the concentration of CO in a gaseous sample.

I2O5 forms iodyl salts, [IO2+], with SO3 and S2O6F2, but iodosyl salts, [IO+], with concentrated sulfuric acid.

Iodine pentoxide decomposes to iodine (vapor) and oxygen when heated to about 350 °C.[4]

References
  1. Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. pp. 851–852. ISBN 978-0-08-037941-8.
  2. Patnaik, P. (2002). Handbook of Inorganic Chemicals. McGraw-Hill. ISBN 0-07-049439-8.
  3. Selte, K.; Kjekshus, A. (1970). "Iodine Oxides: Part III. The Crystal Structure of I2O5" (PDF). Acta Chemica Scandinavica. 24 (6): 1912–1924. doi:10.3891/acta.chem.scand.24-1912.
  4. G. Baxter and G. Tilley, "A Revision of the Atomic Weights of Iodine and Silver," The Chemical News and Journal of Industrial Science; Volumes 99-100, Royal Society Anniversary Meeting, December 3, 1909, p. 276. (Google Books)
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