Iodic acid

Iodic acid, HIO3. It is a white water-soluble solid. Its robustness contrasts with the instability of chloric acid and bromic acid. Iodic acid features iodine in the oxidation state +5 and is one of the most stable oxo-acids of the halogens. When heated, samples dehydrate to give iodine pentoxide. On further heating, the iodine pentoxide further decomposes, giving a mix of iodine, oxygen and lower oxides of iodine.

Iodic acid
Ball-and-stick model of iodic acid
Space-filling model of iodic acid
Names
Other names
Iodic(V) acid
Identifiers
3D model (JSmol)
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard 100.029.056
UNII
Properties
HIO3
Molar mass 175.91 g/mol
Appearance White solid
Density 4.62 g/cm3, solid
Melting point 110 °C (230 °F; 383 K)
269 g/100 mL (20 °C)
Acidity (pKa) 0.75
Conjugate base Iodate
−48.0·10−6 cm3/mol
Hazards
Main hazards acid, corrosive, oxidant
NFPA 704 (fire diamond)
Flash point Non-flammable
Related compounds
Other cations
 Lithium iodate
Potassium iodate
Chloric acid
Bromic acid
Related compounds
 Hydroiodic acid
Iodine pentoxide
Periodic acid
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Preparation

Iodic acid can be produced by oxidizing iodine 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 pKa 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 ions, such as 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. It may be used in preparation of ionization to form alkyl halides.

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, using 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.

Other oxyacids

Iodate is part of a series of oxyacids in which iodine can assume oxidation states of −1, +1, +3, +5, or +7. A number of neutral iodine oxides are also known.

Iodine oxidation state −1 +1 +3 +5 +7
Name Hydrogen iodide Hypoiodous acid Iodous acid Iodic acid Periodic acid
Formula HI HIO HIO2 HIO3 HIO4 or H5IO6


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References
  1. Holleman, Arnold F.; Wiberg, Nils (2007). Lehrbuch der Anorganischen Chemie (in German) (102nd ed.). Berlin. ISBN 978-3-11-017770-1.
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