Iodic acid

Iodic acid
Other names Iodic(V) acid
Identifiers
CAS number	7782-68-5 Y
PubChem	24345
ChemSpider	22761 Y
ChEBI	CHEBI:24857 Y
ChEMBL	CHEMBL1161636 Y
Jmol-3D images	Image 1
SMILES O=I(=O)O
InChI InChI=1S/HIO3/c2-1(3)4/h(H,2,3,4) Y Key: ICIWUVCWSCSTAQ-UHFFFAOYSA-N Y InChI=1/HIO3/c2-1(3)4/h(H,2,3,4) Key: ICIWUVCWSCSTAQ-UHFFFAOYAT
Properties
Molecular formula	HIO3
Molar mass	175.91 g/mol
Appearance	White solid
Density	4.62 g/cm3, solid
Melting point	110 °C
Solubility in water	2.69 kg/l (20 °C)
Acidity (pKa)	0.75
Hazards
EU Index	Not listed
Flash point	Non-flammable
Related compounds
Other cations	Lithium iodate Potassium iodate
Related halogen oxoacids	Chloric acid Bromic acid
Related compounds	Hydroiodic acid Iodine pentoxide Periodic acid
Y (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
Infobox references

Iodic acid, HIO₃, can be obtained as a white solid. It dissolves in water very well, but it also exists in the pure state, as opposed to chloric acid or bromic acid. Iodic acid contains iodine in the oxidation state +5 and it is one of the most stable oxo-acids of the halogens in its pure state. When iodic acid is carefully heated, it dehydrates to iodine pentoxide. On subsequent heating, the iodine pentoxide further decomposes, giving a mix of iodine, oxygen and lower oxides of iodine.

Preparation

Iodic acid can be produced by oxidizing I₂ with strong oxidizers such as Nitric acid HNO
3, Chlorine Cl
2, Chloric acid HClO
3 or Hydrogen peroxide H
2O
2,^[1] for example :

I
2 + 6 H
2O + 5 Cl
2 2 HIO
3 + 10 HCl.

Properties

Iodic acid is a relatively strong acid with a pK_a of 0.75. It is strongly oxidizing in acidic solution, less so in basic solution. When iodic acid acts as oxidizer, then the product of the reaction is either iodine, or iodide ion. Under some special conditions (very low pH and high concentration of chloride ion, e.g. in concentrated hydrochloric acid), iodic acid is reduced to iodine trichloride, a golden yellow compound in solution and no further reduction occurs. In the absence of chloride ions, when there is an excess amount of reductant, then all iodate is converted to iodide ion. When there is an excess amount of iodate, then part of the iodate is converted to iodine.

Uses

Iodic acid is used as a strong acid in analytical chemistry. It may be used to standardize solutions of both weak and strong bases, with methyl red or methyl orange as the indicator.

Use in salt industry

Iodic acid can be used to synthesize sodium or potassium iodate for increasing iodine content of salt.^{[citation needed]}

References

1. ↑ (German) Arnold F. Holleman, Nils Wiberg, « Lehrbuch der Anorganischen Chemie », 102. Auflage, Berlin, 2007.