Difference Between Iron II Chloride and Iron III Chloride

The key difference between iron II chloride and iron III chloride is that the Fe atom in iron(II) chloride chemical compound has a +2 oxidation state whereas the Fe atom in iron(III) chloride compound has a +3 oxidation state.

Iron(II) chloride and iron(III) chloride are important inorganic compounds of the chemical element iron (Fe). Iron II chloride is also named as ferrous chloride, and iron III chloride is named as ferric chloride.

CONTENTS

1. Overview and Key Difference
2. What is Iron II Chloride
3. What is Iron III Chloride
4. Side by Side Comparison – Iron II Chloride vs Iron III Chloride in Tabular Form
5. Summary

What is Iron II Chloride?

Iron(II) chloride is FeCl2, where Fe atom is in +2 oxidation state. It is also named as ferrous chloride. This compound is paramagnetic because it has unpaired electrons that make this compound able to get attracted to an external magnetic field. It is a tan coloured solid with a high melting point. There are two forms of iron(II) chloride as the anhydrous form and the tetrahydrate form. The tetrahydrate form appears in a pale green colour. However, there is a less common dihydrate form as well.

Iron(II) chloride solid can crystalize from water in the form of greenish tetrahydrate. This substance is highly water-soluble, and it gives a pale green solution upon dissolution in water. We can produce the hydrated forms of iron(II) chloride through the treatment of waste from steel production with HCl acid. This type of solutions can be named as spent acid or as pickle liquor. Further, the anhydrous form of this compound can be prepared via adding iron powder to a solution of HCl acid in methanol.

There are different applications of iron(II) chloride, including the production of iron(III) chloride, regeneration of HCl acid through its preparation process, as a coagulation and flocculation agent in wastewater treatment, useful for odour control in wastewater treatment, etc.

What is Iron III Chloride?

Iron(III) chloride is FeCl3, where Fe atom is in +3 oxidation state. It is also named as ferric chloride. This is a common compound of the iron chemical element. It is a crystalline solid having varying colours; the colour depends on the viewing angle, e.g. the crystals appear in dark green colour with reflected light whereas the crystals appear in purple red with transmitted light.

There are three major hydrated forms of iron(III) chloride compound. They are FeCl3.6H2O, FeCl3.2.5H2O, FeCl3.2H2O, and FeCl3.3.5H2O. Characteristically, the aqueous solutions of ferric chloride are yellow coloured.

The anhydrous form of iron(III) chloride can be prepared through the combination of elements where Fe is reacted with Cl2 gas. However, the solutions of ferric chloride can be prepared from iron, and the process includes dissolution of iron ore in HCl acid, followed by the oxidation of iron (II) chloride with chlorine or the oxidation of iron (II) chloride with oxygen gas.

What is the Difference Between Iron II Chloride and Iron III Chloride?

Iron(II) chloride and Iron(III) chloride are inorganic compounds having iron (Fe) and chloride anions bound to each other through ionic bonding. The key difference between iron II chloride and iron III chloride is that the Fe atom in iron(II) chloride chemical compound has +2 oxidation state whereas the Fe atom in iron(III) chloride compound has a +3 oxidation state. Iron(II) chloride has two major forms: dihydrated form and the tetrahydrate form. Iron (III) chloride has four major forms: FeCl3.6H2O, FeCl3.2.5H2O, FeCl3.2H2O, and FeCl3.3.5H2O.

Below infographic shows more differences between iron II chloride and iron III chloride in tabular form.

Summary – Iron II Chloride vs Iron III Chloride

Iron(II) chloride and Iron(III) chloride are inorganic compounds having iron (Fe) and chloride anions bound to each other through ionic bonding.  The key difference between iron II chloride and iron III chloride is that the Fe atom in iron(II) chloride chemical compound has +2 oxidation state whereas the Fe atom in iron(III) chloride compound has a +3 oxidation state.

Reference:

1. “Ferric chloride.” Pubchem, Available here.

Image Courtesy:

1. “Iron(II) chloride anhydrate” By Leiem – Own work (CC BY-SA 4.0) via Commons Wikimedia
2. “Iron(III) chloride anhydrate” By Leiem – Own work (CC BY-SA 4.0) via Commons Wikimedia