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Iron(II) nitrate

Chemical compound From Wikipedia, the free encyclopedia

Iron(II) nitrate

Iron(II) nitrate is the nitrate salt of iron(II). It is commonly encountered as the green hexahydrate, Fe(NO3)2·6H2O, which is a metal aquo complex, however it is not commercially available unlike iron(III) nitrate due to its instability to air. The salt is soluble in water and serves as a ready source of ferrous ions.

Quick Facts Names, Identifiers ...
Iron(II) nitrate
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Hexahydrate
Names
Other names
  • Ferrous nitrate
Identifiers
3D model (JSmol)
ChemSpider
EC Number
  • 233-899-5
UNII
  • Key: MVFCKEFYUDZOCX-UHFFFAOYSA-N
  • InChI=1S/Fe.2NO3/c;2*2-1(3)4/q+2;2*-1
  • hexahydrate: InChI=1S/Fe.2NO3.6H2O/c;2*2-1(3)4;;;;;;/h;;;6*1H2/q+2;2*-1;;;;;;
    Key: SUOTZEJYYPISIE-UHFFFAOYSA-N
  • nonahydrate: InChI=1S/Fe.2NO3.9H2O/c;2*2-1(3)4;;;;;;;;;/h;;;9*1H2/q+2;2*-1;;;;;;;;;
    Key: QZRHHEURPZONJU-UHFFFAOYSA-N
  • [N+](=O)([O-])[O-].[N+](=O)([O-])[O-].[Fe+2]
  • hexahydrate: [N+](=O)([O-])[O-].[N+](=O)([O-])[O-].O.O.O.O.O.O.[Fe+2]
  • nonahydrate: [N+](=O)([O-])[O-].[N+](=O)([O-])[O-].O.O.O.O.O.O.O.O.O.[Fe+2]
Properties
Fe(NO3)2
Molar mass 179.86 g/mol
Appearance Green crystals (hexahydrate)
Melting point 60 °C (140 °F; 333 K)[1] (hexahydrate)
Boiling point 61 °C (142 °F; 334 K)[2] (decomposes)
87.525 g/100 mL
Structure
Orthorhombic[3]
Thermochemistry
−497.9 kJ/mol[2]
Hazards
Lethal dose or concentration (LD, LC):
428 mg/kg (subcutaneous, rabbit)[4]
Related compounds
Other anions
 Iron(II) phosphate
Other cations
 Manganese(II) nitrate
Cobalt(II) nitrate
Related compounds
 Iron(III) nitrate
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Structure

No structure of any salt Fe(NO3)2·xH2O has been determined by X-ray crystallography. Nonetheless, the nature of the aquo complex [Fe(H2O)6]2+ is well known and relatively insensitive to the anion. The Fe-O distances are longer for [Fe(H2O)6]2+ (2.13 Å) than for the ferric analogue [Fe(H2O)6]3+ (1.99 Å).[5] Both [Fe(H2O)6]n+ complexes are high spin, which results in pale colors, paramagnetism, and weak Fe-O bonds.

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The solubility graph of iron(II) nitrate

Production

Iron(II) nitrate can be produced in multiple ways, such as the reaction of iron metal with cold dilute nitric acid:

3 Fe + 8 HNO3 + 12 H2O → 3 Fe(NO3)2(H2O)6 + 2 NO

If this reaction is conducted below -10 °C, nonahydrate is produced. It readily releases water to give the hexahydrate.[2]

The above reaction can also co-produce ferric nitrate. Reacting iron(II) sulfate and lead nitrate under dilute ethanol and then evaporating the solution leads to the formation of the green crystals of the hexahydrate. A solution of iron(II) nitrate is produced by the ion-exchange reaction of iron(II) sulfate and barium nitrate, producing a concentration of up to 1.5 M due to the limited solubility of barium nitrate.[2][6][7]

The solution of the iron(II) nitrate-hydrazine complex is produced by the reaction of hydrazine nitrate and ferric nitrate at 40 °C with copper(II) nitrate as a catalyst:[8]

4 Fe(NO3)3 + N2H5NO3 → 4 Fe(NO3)2 + N2 + 4 HNO3

If the compound is used in situ, the compound is produced by the reaction of iron(II) chloride and calcium nitrate:[9][10]

FeCl2 + Ca(NO3)2 → Fe(NO3)2 + CaCl2

Reactions

The hexahydrate melts at 60 °C and then decomposes at 61 °C into iron(III) oxide rather than iron(II) oxide.[2] A solution of iron(II) nitrate is much more stable, decomposing at 107 °C to iron(III), with the presence of nitric acid lowering the decomposition temperature. Concentrated nitric acid oxidizes iron(II) nitrate into iron(III) nitrate:[6]

3 Fe(NO3)2 + 4 HNO3 → 3 Fe(NO3)3 + NO + 2 H2O

Uses

Iron(II) nitrate has no uses, however, there is a potential use for dye removal.[10][9]

References

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