Difference between revisions of "Iodic acid"
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'''Iodic acid''', HIO<sub>3</sub>, is a moderately strong [[oxoacid]] of [[iodine]]. It forms a series of salts called [[iodate]]s. | '''Iodic acid''', HIO<sub>3</sub>, is a moderately strong [[oxoacid]] of [[iodine]]. It forms a series of salts called [[iodate]]s. | ||
| − | Iodic acid may be prepared by the oxidation of suspensions of iodine in water, either by [[electrolysis]] or with [[nitric acid]].<ref name="G&E"/> Unlike [[Chloric acid|chloric]] and [[bromic acid]]s, it can be isolated as a white crystalline air-stable solid. The solid decomposes on heating, first to HIO<sub>3</sub>·I<sub>2</sub>O<sub>5</sub> at about 100 °C, then to [[iodine pentoxide]] at about 200 °C.<ref name="G&E"/> | + | Iodic acid may be prepared by the oxidation of suspensions of iodine in water, either by [[electrolysis]] or with [[nitric acid]].<ref name="G&E"/> Unlike [[Chloric acid|chloric]] and [[bromic acid]]s, it can be isolated as a white crystalline air-stable solid. The solid decomposes on heating, first to [[anhydro-iodic acid]], HIO<sub>3</sub>·I<sub>2</sub>O<sub>5</sub> or HI<sub>3</sub>O<sub>8</sub>, at about 100 °C, then to [[iodine pentoxide]] at about 200 °C.<ref name="G&E"/> |
Iodic acid is used as [[primary standard]] [[strong acid]] in [[acid–base titration]]s because it can be weighed as a pure solid and has a relatively high [[molar mass]]. However, the solid cannot be dried in a 110 °C oven because of dehydration, and recrystallization is difficult because of the high solubility of HIO<sub>3</sub>: for these reasons, [[potassium biiodate]] is usually preferred as a strong-acid standard. | Iodic acid is used as [[primary standard]] [[strong acid]] in [[acid–base titration]]s because it can be weighed as a pure solid and has a relatively high [[molar mass]]. However, the solid cannot be dried in a 110 °C oven because of dehydration, and recrystallization is difficult because of the high solubility of HIO<sub>3</sub>: for these reasons, [[potassium biiodate]] is usually preferred as a strong-acid standard. | ||
Revision as of 15:28, 10 September 2010
| Iodic acid | |
|---|---|
| IUPAC name | iodic acid |
| Identifiers | |
| InChI | InChI=InChI=1S/HIO3/c2-1(3)4/h(H,2,3,4) |
| InChIKey | ICIWUVCWSCSTAQ-UHFFFAOYAT |
| Standard InChI | InChI=1S/HIO3/c2-1(3)4/h(H,2,3,4) |
| Standard InChIKey | ICIWUVCWSCSTAQ-UHFFFAOYSA-N |
| CAS number | [] |
| EC number | |
| ChemSpider | |
| Properties[1][2] | |
| Chemical formula | HIO3 |
| Molar mass | 175.91 g mol−1 |
| Appearance | white crystals |
| Density | 4.629 g cm−3 |
| Melting point |
100 °C decomp. |
| Solubility in water | 286 g/100 ml (0 °C) 473 g/100 ml (80 °C) |
| Acidity (pKa) | 0.804 |
| Structure[1] | |
| Molecular geometry | pyramidal; r(I=O) = 181 pm, r(I–OH) = 189 pm, O=I=O = 101.4°, O=I–OH = 97° |
| Hazards[3] | |
| EU index number | not listed |
| GHS pictograms |  
|
| GHS signal word | DANGER |
| GHS hazard statements | H272, H314, H318 |
| GHS precautionary statements | P210, P220, P221, P260, P264, P280, P301+330+331, P303+361+353, P363, P304+340, P310, P321, P305+351+338, P370+378 |
| Flash point | non-flammable |
| Related compounds | |
| Other anions | Hydriodic acid Periodic acid |
| Other compounds | Chloric acid Bromic acid |
| Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) | |
Iodic acid, HIO3, is a moderately strong oxoacid of iodine. It forms a series of salts called iodates.
Iodic acid may be prepared by the oxidation of suspensions of iodine in water, either by electrolysis or with nitric acid.[1] Unlike chloric and bromic acids, it can be isolated as a white crystalline air-stable solid. The solid decomposes on heating, first to anhydro-iodic acid, HIO3·I2O5 or HI3O8, at about 100 °C, then to iodine pentoxide at about 200 °C.[1]
Iodic acid is used as primary standard strong acid in acid–base titrations because it can be weighed as a pure solid and has a relatively high molar mass. However, the solid cannot be dried in a 110 °C oven because of dehydration, and recrystallization is difficult because of the high solubility of HIO3: for these reasons, potassium biiodate is usually preferred as a strong-acid standard.
Notes and references
Notes
References
- ↑ 1.0 1.1 1.2 1.3 Greenwood, Norman N.; Earnshaw, A. Chemistry of the Elements; Pergamon: Oxford, 1984; p 1010. ISBN 0-08-022057-6.
- ↑ CRC Handbook of Chemistry and Physics, 62nd ed.; Weast, Robert C., Ed.; CRC Press: Boca Raton, FL, 1981; p B-106. ISBN 0-8493-0462-8.
- ↑ HSNO Chemical Classification Information Database, <http://www.ermanz.govt.nz/Chemicals/ChemicalDisplay.aspx?SubstanceID=12620> (accessed 9 September 2010), New Zealand Environmental Risk Management Authority.
External links
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See also the corresponding article on Wikipedia. |
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