Iron(II) hydroxide: Difference between revisions
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| Name = Iron(II) hydroxide |
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| ImageFile = Hydroxid železnatý.PNG |
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| ImageFile1 = Mg(OH)2Xray.jpg |
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| IUPACName = Iron(II) hydroxide |
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| ImageName = Iron(II) hydroxide |
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| OtherNames = Ferrous hydroxide, green rust |
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| SystematicName = |
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| ChemSpiderID = 8305416 |
| ChemSpiderID = 8305416 |
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| UNII_Ref = {{fdacite|correct|FDA}} |
| UNII_Ref = {{fdacite|correct|FDA}} |
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| InChI = 1/Fe.2H2O/h;2*1H2/q+2;;/p-2 |
| InChI = 1/Fe.2H2O/h;2*1H2/q+2;;/p-2 |
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| InChIKey = NCNCGGDMXMBVIA-NUQVWONBAV |
| InChIKey = NCNCGGDMXMBVIA-NUQVWONBAV |
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| SMILES = [Fe |
| SMILES = O[Fe]O |
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| StdInChI_Ref = {{stdinchicite|correct|chemspider}} |
| StdInChI_Ref = {{stdinchicite|correct|chemspider}} |
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| StdInChI = 1S/Fe.2H2O/h;2*1H2/q+2;;/p-2 |
| StdInChI = 1S/Fe.2H2O/h;2*1H2/q+2;;/p-2 |
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| StdInChIKey = NCNCGGDMXMBVIA-UHFFFAOYSA-L |
| StdInChIKey = NCNCGGDMXMBVIA-UHFFFAOYSA-L |
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| CASNo = 18624-44-7 |
| CASNo = 18624-44-7 |
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| CASNo_Ref = {{cascite|correct|CAS}} |
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| PubChem = 10129897 |
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| Section2 = {{Chembox Properties |
| Section2 = {{Chembox Properties |
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| Formula = Fe(OH)<sub>2</sub> |
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| MolarMass = 89.86 g/mol |
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| Appearance = green solid |
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| Density = 3.4 g/cm<sup>3</sup> <ref>{{RubberBible87th}}</ref> |
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| Solubility = 0.000052 g/100 g water (20 °C, pH 7)<ref>CRC Handbook of Chemistry and Physics, 84th Edition, CRC Press, 2004, pg 4-62</ref> |
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| SolubilityProduct = 8.0 x 10<sup>−16</sup><ref>{{cite journal |last1=Stumm |first1=Werner |last2=Lee |first2=G. F. |title=Oxygenation of Ferrous Iron |journal=Industrial & Engineering Chemistry |date=February 1961 |volume=53 |issue=2 |pages=143–146 |doi=10.1021/ie50614a030 |url=https://www.gfredlee.com/SurfaceWQ/StummOxygenFerrous.pdf |access-date=17 November 2022 |language=en}}</ref> |
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| SolubilityProduct = 8.0 x 10<sup>-16</sup> |
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| pKa = 17<ref name=P82db>{{cite book|title=Ionisation Constants of Inorganic Acids and Bases in Aqueous Solution|editor-first=D. D.|editor-last=Perrin|edition=2<sup>nd</sup>|series=[[IUPAC]] Chemical Data|issue=29|publisher=Pergamon|location=Oxford|year=1982|publication-date=1984|orig-date=1969|lccn=82-16524|isbn=0-08-029214-3|at=Entry 130}}</ref> |
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| Section3 = {{Chembox Hazards |
| Section3 = {{Chembox Hazards |
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[[File:DSC01968 - Fe (II) Reactions.JPG|thumb|left|The second tube from the left has almost pure whitish iron(II) hydroxide.]] |
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[[File:Ferrous hydroxide.JPG|thumb|left|This container has a precipitate of dark greenish iron(II) hydroxide in it.]] |
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'''Iron(II) hydroxide''' or '''ferrous hydroxide''' is a [[Chemical compound|compound]] produced when iron(II) ions, from a compound such as [[iron(II) sulfate]], react with [[hydroxide]] ions. Iron(II) hydroxide itself is practically white, but even traces of oxygen impart it with a greenish tinge. If the solution was not deoxygenated and the iron reduced, the precipitate can vary in color starting from green to reddish brown depending on the iron(III) content. This precipitate is also known as "green rust" in the crystal lattice of which iron(II) ions are easily substituted by iron(III) ions produced by its progressive oxidation. In the presence of oxygen the color changes quickly. Green rust is a powerful reducing agent and also a [[Layered double hydroxides|layer double hydroxide]] (LDH) capable to sorb anions because of the presence of positive electrical charges borne on its surface. The mineralogical form of green rust is a recently discovered [[fougerite]]. All forms of green rust (including fougerite) are more complex and variable than the ideal iron(II) hydroxide compound. The natural analogue of iron(II) hydroxide compound is a very rare mineral [[amakinite]], (Fe,Mg)(OH)<sub>2</sub>. |
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'''Iron(II) hydroxide''' or '''ferrous hydroxide''' is an [[inorganic compound]] with the formula Fe(OH)<sub>2</sub>. It is produced when iron(II) salts, from a compound such as [[iron(II) sulfate]], are treated with [[hydroxide]] ions. Iron(II) hydroxide is a white solid, but even traces of oxygen impart a greenish tinge. The air-oxidised solid is sometimes known as "[[green rust]]". |
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Iron(II) hydroxide is poorly soluble (1.43 × 10<sup>−3</sup> [[gram|g]]/[[liter|L]]). It precipitates from the reaction of iron(II) sulfate and hydroxide ions (from a soluble compound containing hydroxide ion): |
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==Preparation and reactions== |
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Iron(II) hydroxide is poorly [[solubility|soluble]] in water (1.43 × 10<sup>−3</sup> [[gram|g]]/[[liter|L]]), or 1.59 × 10<sup>−5</sup> mol/L. <!-- (Commenting out this sentence left by an anonymous editor; no idea if there is a problem here or not; see Talk page) somehow these values don't match the ones in the table on the right. Someone please verify where the 0,72 g/100mL comes from --> It [[precipitation|precipitates]] from the reaction of iron(II) and [[hydroxide]] salts:<ref name=brauer>H. Lux "Iron(II) Hydroxide" in Handbook of Preparative Inorganic Chemistry, 2nd Ed. Edited by G. Brauer, Academic Press, 1963, NY. Vol. 1. p. 1498.</ref> |
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If the solution is not [[Deoxygenation|deoxygenated]] and iron not totally reduced in Fe(II), the precipitate can vary in colour starting from green to reddish brown depending on the iron(III) content. Iron(II) ions are easily substituted by iron(III) ions produced by its progressive [[oxidation]]. |
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⚫ | It is also easily formed as |
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==Ageing and transformation into magnetite== |
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==Structure== |
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Fe(OH)<sub>2</sub> adopts the [[brucite]] structure, i.e. the arrangement of the atoms in the crystal are the same as the arrangement of the atoms in Mg(OH)<sub>2</sub>. The Fe(II) centers are bonded to six hydroxide [[ligand]]s. Each hydroxide ligand [[bridging ligand|bridges]] to three Fe(II) sites. The O-H bonds are perpendicular to the planes defined by the oxygen atoms, projecting above and below these layers.<ref>{{cite journal |doi=10.1016/0022-2860(94)08355-x |title=Lattice vibration spectra. Part LXXXII. Brucite-type hydroxides M(OH)2 (M = Ca, Mn, Co, Fe, Cd) — IR and Raman spectra, neutron diffraction of Fe(OH)2 |date=1994 |last1=Lutz |first1=H.D. |last2=Möller |first2=H. |last3=Schmidt |first3=M. |journal=Journal of Molecular Structure |volume=328 |pages=121–132 }}</ref> |
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==Reactions== |
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The well crystallized iron(II,III) oxide (Fe<sub>3</sub>O<sub>4</sub>) is thermodynamically more stable than the iron(II) hydroxide. |
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==Uses== |
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==Natural occurrence== |
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⚫ | Iron(II) hydroxide has also been investigated as an agent for the removal of toxic [[selenate]] and [[selenous acid|selenite]] ions from water systems such as [[wetland]]s. The iron(II) hydroxide [[redox|reduces]] these ions to elemental [[selenium]], which is insoluble in water and [[precipitation (chemistry)|precipitates]] out.<ref>{{cite journal |
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[[Image:Limestone building with pollution.jpg|thumb|left|Iron III hydroxide staining caused by oxidation of dissolved iron II and precipitation, [[Perth]], [[Western Australia]].]] |
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| last = Zingaro |
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Iron dissolved in [[groundwater]] is in the reduced iron II form. If this groundwater comes in contact with oxygen at the surface, e.g. in natural [[Spring (hydrology)|springs]], iron II is oxidised to iron III and forms insoluble hydroxides in water.<ref>[https://www.lenntech.com/groundwater/iron.htm lenntech.com]</ref> |
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| first = Ralph A. |
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The natural analogue of iron(II) hydroxide compound is the very rare mineral [[amakinite]], {{chem2|(Fe,Mg)(OH)2}}.<ref name=Mindat>{{Cite web|url=https://www.mindat.org/min-180.html|title = Amakinite}}</ref><ref name=IMA>{{Cite web|url=https://www.ima-mineralogy.org/Minlist.htm|title=List of Minerals|date=21 March 2011}}</ref> |
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| coauthors = ''et al.'' |
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| year = 1997 |
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| title = Reduction of oxoselenium anions by iron(II) hydroxide |
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| journal = Environment International |
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| volume = 23 |
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| issue = 3 |
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| pages = 299–304 |
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| doi = 10.1016/S0160-4120(97)00032-9 |
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}}</ref> |
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== Application == |
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Note: pK<sub>sp</sub> = 15.097 where p is the -log and K<sub>sp</sub> is the Solubility Product Constant. This means it has a low tendency to dissolve, but is not entirely insoluble. An acidic solution would allow this to disassociate more because the H<sup>+</sup> would react with the OH<sup>-</sup> in the compound. |
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⚫ | Iron(II) hydroxide has also been investigated as an agent for the removal of toxic [[selenate]] and [[selenous acid|selenite]] ions from water systems such as [[wetland]]s. The iron(II) hydroxide [[redox|reduces]] these ions to elemental [[selenium]], which is insoluble in water and [[precipitation (chemistry)|precipitates]] out.<ref>{{cite journal |last=Zingaro |first=Ralph A. |display-authors=etal |date=1997 |title=Reduction of oxoselenium anions by iron(II) hydroxide |journal=Environment International |volume=23 |issue=3 |pages=299–304 |doi=10.1016/S0160-4120(97)00032-9}}</ref> |
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In a basic solution iron(II) hydroxide is the electrochemically active material of the negative electrode of the [[nickel-iron battery]]. |
In a basic solution iron(II) hydroxide is the electrochemically active material of the negative electrode of the [[nickel-iron battery]]. |
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==See also== |
==See also== |
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* [[Rust]] |
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* [[Layered double hydroxides]] |
* [[Layered double hydroxides]] |
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* [[Periodic table]] |
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==References== |
==References== |
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{{Iron compounds}} |
{{Iron compounds}} |
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{{Hydroxides}} |
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[[Category: |
[[Category:Iron(II) compounds]] |
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[[Category:Iron compounds]] |
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[[Category:Hydroxides]] |
[[Category:Hydroxides]] |
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[[Category:Materials]] |
[[Category:Materials]] |
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[[fr:Hydroxyde de fer]] |
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[[ar:هيدروكسيد الحديد الثنائي]] |
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[[hu:Vas(II)-hidroxid]] |
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[[nl:IJzer(II)hydroxide]] |
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[[no:Jernhydroksid]] |
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[[pt:Hidróxido de ferro (II)]] |
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[[ru:Гидроксид железа(II)]] |
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[[simple:Iron(II) hydroxide]] |
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[[sv:Järn(II)hydroxid]] |
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[[zh:氢氧化亚铁]] |