Iodic acid

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Iodic acid
Iodic acid.svg
Ball-and-stick model of iodic acid Iodic-acid-gamma-polymorph-side-3D-bs-17.png
Ball-and-stick model of iodic acid
Space-filling model of iodic acid Iodic-acid-gamma-polymorph-side-3D-sf.png
Space-filling model of iodic acid
Names
Other names
Iodic(V) acid
Identifiers
3D model (JSmol)
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard 100.029.056 OOjs UI icon edit-ltr-progressive.svg
PubChem CID
UNII
  • InChI=1S/HIO3/c2-1(3)4/h(H,2,3,4) Yes check.svgY
    Key: ICIWUVCWSCSTAQ-UHFFFAOYSA-N Yes check.svgY
  • InChI=1/HIO3/c2-1(3)4/h(H,2,3,4)
    Key: ICIWUVCWSCSTAQ-UHFFFAOYAT
  • O[I+2]([O-])[O-]
Properties
HIO3
Molar mass 175.91 g/mol
AppearanceWhite 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 [1]
Conjugate base Iodate
48.0·10−6 cm3/mol
Hazards
Occupational safety and health (OHS/OSH):
Main hazards
acid, corrosive, oxidant
GHS labelling: [2]
GHS-pictogram-rondflam.svg GHS-pictogram-acid.svg
Danger
NFPA 704 (fire diamond)
NFPA 704.svgHealth 3: Short exposure could cause serious temporary or residual injury. E.g. chlorine gasFlammability 0: Will not burn. E.g. waterInstability 1: Normally stable, but can become unstable at elevated temperatures and pressures. E.g. calciumSpecial hazard OX: Oxidizer. E.g. potassium perchlorate
3
0
1
OX
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
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Yes check.svgY  verify  (what is  Yes check.svgYX mark.svgN ?)

Iodic acid is a white water-soluble solid with the chemical formula HIO3. 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.

Contents

Preparation

Iodic acid can be produced by oxidizing I2 with strong oxidizers such as HNO3, Cl2, HClO3 or H2O2, [3] for example:

I2 + 6 H2O + 5Cl2 ⇌ 2 HIO3 + 10 HCl

Iodic acid is also produced by the reaction of iodine monochloride with water:

5 ICl + 3 H2O → 5 HCl + HIO3 + 2 I2

Structure

Iodic acid crystallises from acidic solution as orthorhombic α-HIO
3
in space group P212121. The structure consists of pyramidal molecules linked by hydrogen bonding and intermolecular iodine-oxygen interactions. The I=O bond lengths are 1.81 Å while the I–OH distance is 1.89 Å. [4] [5] [6] Several other polymorphs have been reported, including an orthorhombic γ form in space group Pbca [7] and an orthorhombic δ form in space group P212121. [8] All of the polymorphs contain pyramidal molecules, hydrogen bonding and I···O interactions, but differ in packing arrangement.

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.[ citation needed ] 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.[ citation needed ]

Other oxyacids

Iodic acid 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
FormulaHIHIOHIO2HIO3HIO4 or H5IO6

Related Research Articles

<span class="mw-page-title-main">Iodine</span> Chemical element with atomic number 53 (I)

Iodine is a chemical element; it has symbol I and atomic number 53. The heaviest of the stable halogens, it exists at standard conditions as a semi-lustrous, non-metallic solid that melts to form a deep violet liquid at 114 °C (237 °F), and boils to a violet gas at 184 °C (363 °F). The element was discovered by the French chemist Bernard Courtois in 1811 and was named two years later by Joseph Louis Gay-Lussac, after the Ancient Greek Ιώδης, meaning 'violet'.

<span class="mw-page-title-main">Nitrous acid</span> Chemical compound

Nitrous acid is a weak and monoprotic acid known only in solution, in the gas phase, and in the form of nitrite salts. It was discovered by Carl Wilhelm Scheele, who called it "phlogisticated acid of niter". Nitrous acid is used to make diazonium salts from amines. The resulting diazonium salts are reagents in azo coupling reactions to give azo dyes.

<span class="mw-page-title-main">Hydrogen iodide</span> Chemical compound

Hydrogen iodide (HI) is a diatomic molecule and hydrogen halide. Aqueous solutions of HI are known as hydroiodic acid or hydriodic acid, a strong acid. Hydrogen iodide and hydroiodic acid are, however, different in that the former is a gas under standard conditions, whereas the other is an aqueous solution of the gas. They are interconvertible. HI is used in organic and inorganic synthesis as one of the primary sources of iodine and as a reducing agent.

<span class="mw-page-title-main">Iodate</span> Polyatomic anion (IO3) with charge -1

An iodate is the polyatomic anion with the formula IO−3. It is the most common form of iodine in nature, as it comprises the major iodine-containing ores. Iodate salts are often colorless. They are the salts of iodic acid.

Iodometry, known as iodometric titration, is a method of volumetric chemical analysis, a redox titration where the appearance or disappearance of elementary iodine indicates the end point.

<span class="mw-page-title-main">Iodine clock reaction</span> Experiment to show chemical kinetics in action

The iodine clock reaction is a classical chemical clock demonstration experiment to display chemical kinetics in action; it was discovered by Hans Heinrich Landolt in 1886. The iodine clock reaction exists in several variations, which each involve iodine species and redox reagents in the presence of starch. Two colourless solutions are mixed and at first there is no visible reaction. After a short time delay, the liquid suddenly turns to a shade of dark blue due to the formation of a triiodide–starch complex. In some variations, the solution will repeatedly cycle from colorless to blue and back to colorless, until the reagents are depleted.

<span class="mw-page-title-main">Briggs–Rauscher reaction</span> Oscillating chemical reaction

The Briggs–Rauscher oscillating reaction is one of a small number of known oscillating chemical reactions. It is especially well suited for demonstration purposes because of its visually striking colour changes: the freshly prepared colourless solution slowly turns an amber colour, then suddenly changes to a very dark blue. This slowly fades to colourless and the process repeats, about ten times in the most popular formulation, before ending as a dark blue liquid smelling strongly of iodine.

<span class="mw-page-title-main">Potassium iodate</span> Chemical compound

Potassium iodate (KIO3) is an ionic inorganic compound with the formula KIO3. It is a white salt that is soluble in water.

<span class="mw-page-title-main">Sodium iodate</span> Chemical compound

Sodium iodate (NaIO3) is the sodium salt of iodic acid. Sodium iodate is an oxidizing agent. It has several uses.

<span class="mw-page-title-main">Iodine monochloride</span> Chemical compound

Iodine monochloride is an interhalogen compound with the formula ICl. It is a red-brown chemical compound that melts near room temperature. Because of the difference in the electronegativity of iodine and chlorine, this molecule is highly polar and behaves as a source of I+. Discovered in 1814 by Gay-Lussac, iodine monochloride is the first interhalogen compound discovered.

Osmium compounds are compounds containing the element osmium (Os). Osmium forms compounds with oxidation states ranging from −2 to +8. The most common oxidation states are +2, +3, +4, and +8. The +8 oxidation state is notable for being the highest attained by any chemical element aside from iridium's +9 and is encountered only in xenon, ruthenium, hassium, iridium, and plutonium. The oxidation states −1 and −2 represented by the two reactive compounds Na
2
[Os
4
(CO)
13
]
and Na
2
[Os(CO)
4
]
are used in the synthesis of osmium cluster compounds.

Iodine compounds are compounds containing the element iodine. Iodine can form compounds using multiple oxidation states. Iodine is quite reactive, but it is much less reactive than the other halogens. For example, while chlorine gas will halogenate carbon monoxide, nitric oxide, and sulfur dioxide, iodine will not do so. Furthermore, iodination of metals tends to result in lower oxidation states than chlorination or bromination; for example, rhenium metal reacts with chlorine to form rhenium hexachloride, but with bromine it forms only rhenium pentabromide and iodine can achieve only rhenium tetraiodide. By the same token, however, since iodine has the lowest ionisation energy among the halogens and is the most easily oxidised of them, it has a more significant cationic chemistry and its higher oxidation states are rather more stable than those of bromine and chlorine, for example in iodine heptafluoride.

Iron shows the characteristic chemical properties of the transition metals, namely the ability to form variable oxidation states differing by steps of one and a very large coordination and organometallic chemistry: indeed, it was the discovery of an iron compound, ferrocene, that revolutionalized the latter field in the 1950s. Iron is sometimes considered as a prototype for the entire block of transition metals, due to its abundance and the immense role it has played in the technological progress of humanity. Its 26 electrons are arranged in the configuration [Ar]3d64s2, of which the 3d and 4s electrons are relatively close in energy, and thus it can lose a variable number of electrons and there is no clear point where further ionization becomes unprofitable.

The Bray–Liebhafsky reaction is a chemical clock first described by William C. Bray in 1921 and the first oscillating reaction in a stirred homogeneous solution. He investigated the role of the iodate, the anion of iodic acid, in the catalytic conversion of hydrogen peroxide to oxygen and water by the iodate. He observed that the concentration of iodine molecules oscillated periodically and that hydrogen peroxide was consumed during the reaction.

<span class="mw-page-title-main">Hypoiodous acid</span> Chemical compound

Hypoiodous acid is an inorganic compound with the chemical formula HOI. It forms when an aqueous solution of iodine is treated with mercuric or silver salts. It rapidly decomposes by disproportionation:

<span class="mw-page-title-main">Iodine pentoxide</span> Chemical compound

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

<span class="mw-page-title-main">Manganese(II) iodide</span> Chemical compound

Manganese(II) iodide is the chemical compound composed of manganese and iodide with the formula MnI2(H2O)n. The tetrahydrate is a pink solid while the anhydrous derivative is beige. Both forms feature octahedral Mn centers. Unlike MnCl2(H2O)4 and MnBr2(H2O)4 which are cis, MnI2(H2O)4 is trans.

<span class="mw-page-title-main">Tetraiodine nonoxide</span> Chemical compound

Tetraiodine nonoxide is an iodine oxide with the chemical formula I4O9.

Diiodine tetraoxide, I2O4, is a chemical compound of oxygen and iodine. It belongs to the class of iodine oxides, and is a mixed oxide, consisting of iodine(III) and iodine(V) oxidation states.

Diiodosyl sulfate is an inorganic compound, a basic salt of iodine and sulfuric acid with the formula (IO)2SO4. It forms yellow crystals.

References

  1. Perrin, D. D., ed. (1982) [1969]. Ionisation Constants of Inorganic Acids and Bases in Aqueous Solution. IUPAC Chemical Data (2nd ed.). Oxford: Pergamon (published 1984). Entry 127. ISBN   0-08-029214-3. LCCN   82-16524.
  2. "Iodic acid" (PDF).
  3. Holleman, Arnold F.; Wiberg, Nils (2007). Lehrbuch der Anorganischen Chemie (in German) (102nd ed.). Berlin. ISBN   978-3-11-017770-1.{{cite book}}: CS1 maint: location missing publisher (link)
  4. Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. p. 863. ISBN   978-0-08-037941-8.
  5. Rogers, Max T.; Helmholz, Lindsay (1941). "The Crystal Structure of Iodic Acid". J. Am. Chem. Soc. 63 (1): 278–284. doi:10.1021/ja01846a068.
  6. Ståhl, Kenny; Szafranski, Marek (1992). "A Single-Crystal Neutron Diffraction Study of HIO3 at 295 and 30 K and of DIO3 at 295 K". Acta Chem. Scand. 46: 1146–1148. doi: 10.3891/acta.chem.scand.46-1146 .
  7. Fischer, Andreas; Lindsjö, Martin (2005). "γ-HIO3 – a Metastable, Centrosymmetric Polymorph of Iodic Acid". Z. Anorg. Allg. Chem. 631 (9): 1574–1576. doi:10.1002/zaac.200500099.
  8. Wu, Tao; Zavalij, Peter Y.; Zachariah, Michael R. (2017). "Crystal structure of a new polymorph of iodic acid, δ-HIO3, from powder diffraction". Powder Diffraction . 32 (4): 261–264. Bibcode:2017PDiff..32..261W. doi:10.1017/S0885715617000859. S2CID   104100313.