Iodic acid
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2008-06-30T16:36:55Z
BrentN
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{{Chembox new
| Name = Iodic acid
| ImageFile = Iodic-acid-2D.png
<!-- | ImageSize = 200px -->
| ImageName = Iodic acid
| ImageFileL1 = Iodic-acid-3D-balls.png
<!-- | ImageSize:1 = 100px -->
| ImageNameL1 = Ball-and-stick model of iodic acid
| ImageFileR1 = Iodic-acid-3D-vdW.png
<!-- | ImageSizeR1 = 100px -->
| ImageNameR1 = Space-filling model of iodic acid
| OtherNames = Iodic(V) acid
| Section1 = {{Chembox Identifiers
| CASNo = 7782-68-5
}}
| Section2 = {{Chembox Properties
| Formula = HIO<sub>3</sub>
| MolarMass = 175.91 g/mol
| Appearance = white solid
| Density = 4.62 g/cm<sup>3</sup>, solid
| Solubility = 269 g/100 ml (20 °C)
| MeltingPt = 110 °C
| BoilingPt =
| pKa = 0.75
}}
| Section3 = {{Chembox Structure
| MolShape =
| Dipole =
}}
| Section7 = {{Chembox Hazards
| ExternalMSDS =
| EUClass = not listed
| FlashPt = non flammable
}}
| Section8 = {{Chembox Related
| OtherAnions = [[Hydriodic acid]]<br />[[Periodic acid]]
| OtherCations = [[Potassium iodate]]
| Function = [[oxoacid]]s
| OtherFunctn = [[Chloric acid]]<br />[[Bromic acid]]
| OtherCpds = [[Iodine pentoxide]]
}}
}}
'''Iodic acid''', HIO<sub>3</sub>, 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, then it loses water, and iodine pentoxide remains behind. On stronger 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]] I<sub>2</sub> with [[chlorine]] in an aqueous solution.
==Properties==
Iodic acid is a relatively [[strong acid]] with a [[Acid dissociation constant|p''K''<sub>a</sub>]] 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 reductor, 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 [[analytical standard|standard]] [[strong acid]] in [[analytical chemistry]]. It may be used to standardize solutions of both [[weak base|weak]] and [[strong base]]s, with [[methyl red]] or [[methyl orange]] as the [[pH indicator|indicator]].
==References==
{{Unreferenced|date =September 2007}}
<references/>
[[Category:Iodates]]
[[Category:Acids]]
[[Category:Analytical standards]]
[[cs:Kyselina jodičná]]
[[de:Iodsäure]]
[[es:Ácido yódico]]
[[fr:Acide iodique]]
[[it:Acido iodico]]
[[ja:ヨウ素酸]]
[[ru:Иодноватая кислота]]
[[fi:Jodihappo]]
[[zh:碘酸]]