Thiocyanatoiron

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Thiocyanatoiron
Pentaaquathiocyanatoiron(II)-3D-balls.png
Names
IUPAC name
pentaaquathiocyanatoiron(III)
Other names
ferric thiocyanate
iron(III) thiocyanate
Properties
CFeH10NO5S
Molar mass 204.0048
Except where noted otherwise, data is given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
Infobox references

Thiocyanatoiron (systematically named thiocyanatoiron(2+)) is a inorganic cation with the chemical formula [Fe(SCN)]2+. It is known to produce a blood red color in solution. This is used as a test for Fe3+ in the laboratory. Fe3+ reacts with thiocyanate to give a series of intensely red colored compounds which remain in the solution and does not undergo any reaction after the formation of the stable octahedral structure. In high concentration of SCN the compound is fairly octahedral with six thiocyanate ligands bonded to iron atom. Thiocyanatoiron forms a pentahydrate.

Thiocyanatoiron must be stored in an acidic solution to prevent the formation of FeOH2+ ions. The excess H+ ions in the acidic solution prevent Fe3+ from engaging in side reactions. Thiocyanatoiron decomposes with exposure to light. The thiocyanatoiron ion is usually formed through an equilibrium reaction:

Fe3+(aq) + SCN(aq) ↔ [Fe(SCN)]2+(aq)

Chemical properties[edit]

Acidity[edit]

The iron(III) segment in thiocyanatoiron(III)s such as thiocyanatoiron can assimilate a hydroxide into the molecule by substitution:

FeSCN2+ + OH → FeOH2+ + SCN

Because of this capture of a hydroxide (OH), thiocyanatoiron has Arrhenius acidic character. In aqueous solution, most thiocyanatoiron is hydrolyzed.

FeSCN2+ + H2O is in a favored equilibrium with FeOH2+ + HSCN

Chemical reactions[edit]

Thiocyanatoiron undergoes the typical chemical reactions of a thiocyanatoiron(III). Upon treatment with a standard base, it converts to dihydroxyiron(III) or trihydroxyiron(III), and metal thiocyanate. Reduction of thiocyanatoiron(III) gives thiocyanatoiron(II).

References[edit]

  • Advanced Chemistry with Vernier, Lab Quest 10