What is Fe₃O₄ Iron Oxide?

Fe₃O4 is an Iron(II, III) Oxide. Fe3O4 is also called Magnetite which is an Iron Ore. It is formed by the combination of Iron(II) Oxide and Iron (III) Oxide i.e. FeO and Fe₂O₃, respectively. Iron oxide is made up of iron and oxygen molecules. They are one of the most commonly occurring compounds in nature. Iron oxide is also known as Black iron oxide due to the physical appearance of the compound. Fe₃O₄ is one of the many oxides formed by iron. Iron oxide ( Fe₃O₄ ) is most commonly used as black pigment. It has a metallic glow and a deep black colour.

Magnetite Formula

Magnetite is one of the iron ores found in the earth’s crust. The formula of magnetite is given as

Molecular Formula of Magnetite is Fe₃O₄

Iron (II, III) Oxide Structure

Iron Oxide ( Fe₃O₄) molecule consists of Iron and oxygen atoms in its structure. The chemical formula of Iron (II, III) Oxide is Fe₃O₄. This means that an Iron oxide molecule consists of 3 oxygen molecules and 4 oxygen molecules. The bond formed between the atoms of iron and oxygen is ionic this is due to the metallic nature of iron and the non-metallic nature of oxygen atoms. It is due to the electronegativity difference in atoms of metallic and non-metallic atoms. The structure of Fe3O4 Iron Oxide is a cubic inverse spinel structure.

Fe₃O₄ Properties

Properties of Fe3O4 can be classified into two types:

• Physical Properties of Fe₃O₄
• Chemical Properties of Fe₃O₄

Physical Properties of Iron Oxide ( Fe₃O₄)

Physical properties of Fe3O4 is mentioned below:

• It has a dark black appearance, it is called Mars black due to the colour.
• It is present in powder or a solid form.
• It is an orderless powder when stored at room temperature.
• It has high electric conductivity.

Chemical Properties of Iron Oxide ( Fe₃O₄)

Chemical properties of Iron(ii, iii) oxide is mentioned below:

• Melting point of iron(ii, iii) oxide is 1597 ℃
• Boiling point of iron(ii, iii) oxide is 2623 ℃
• Molecular mass of iron(ii, iii) oxide is 231 g/mol
• It is ferrimagnetic
• It can be used for the production of brown pigment which is used in dye. This is the controlled oxidation of Iron Oxide. The formed compound is known as Maghnemite.

2Fe₃O₄ + 1/2 O₂ → 3???? – Fe₂O₃

• The continuous calcination of Iron oxide leads to the formation of red Pigment. The end product of the reaction is known as Hematite.

2Fe₃O4 + 1/2 O₂ → 3α – Fe₂O₃

• Reduction of Fe3O4 or the magnetite ore with carbon monoxide leads to production of steel

Fe₃O₄ + 4CO → 3Fe + 4CO₂

Oxidation Number of Fe₃O₄

In Fe₃O₄, we find the oxidation number of element in it particularly that of Fe. As we know iron oxide Fe₃O₄ is a mixture of Fe₂O₃ and FeO. So the oxidation number of any element in Fe₂O₄ will be average of both the compounds.

• In Fe₂O₃ the oxidation sate of iron is 3
• In FeO the oxidation number of Fe is 2

Therefore the average oxidation sates of Iron Oxide is (3+3+2)/2 = 8/3

We can also find the oxidation number of Fe in Fe3O4 in the following manner:

Let Oxidation Number of Fe is x

• We know that Oxidation Number of O is -2
• Since, Fe3O4 is neutral, hence overall charge is zero

Therefore, 3x + 4(-2) = 0

⇒ 3x -8 = 0

⇒ x = +8/3

Preparation of Fe₃O₄

Though iron oxide Fe₃O₄ exists naturally its high usage of has lead to the wide-scale production of this compound. Below are a few methods of Iron oxide production:

Method 1

The reaction between Hot iron metal and steam, this reaction results in iron oxide and hydrogen gas

3Fe + 4H₂O → Fe₃O₄ + 4 H₂

Method 2

It can be produced by Schiorr reaction. Under a low concentration of oxygen, Freous Hydroxide can be broken down to form iron oxide, water molecules and hydrogen gas.

3Fe(OH)₂ → Fe₃O₄ + H₂ + 2H₂O

Method 3

Iron oxide is commercially produced with the use of scrap iron and industrial waste. The said materials contain huge amounts of iron salts which are used in the production of Iron oxide. This process is also called Laux Process

C₆H₅NO₂+ 3Fe + 2H₂O → C₆H₅NH₂ + Fe3O4

Applications of Fe₃O₄ Iron Oxide

Fe₃O₄ Iron Oxide is used for following purposes

• Iron Oxide is widely used in black pigments due to its black colour.
• Iron Oxide is used as a catalyst in Haber’s process, increasing the rate of the reaction.
• Iron Oxide is an important component of MRI scanning as they act as contrasting agents.
• It is widely used in the production of other products like plastic, ink and paint industry.
• NanoParticles of iron Oxide are used for drug delivery and Biosensing.
• It is used as a protective layer for steel, preventing it from rusting.This process is known as Bluing.

Also, Check

• Iron Oxide Formula
• Iron II Oxide Formula
• Iron (III) Oxide Formula
• Iron III Hydroxide Formula

Fe₃O₄ Iron Oxide Frequently Asked Question

What is Fe₃O₄ Iron Oxide also called?

Fe₃O₄ Iron Oxide is also called Magnetite

What is Schiorr Reaction?

Schiorr’s Reaction is used to produce Fe₃O₄. In this reaction, Ferrous Hydroxide breaks down to produce Hydrogen gas and Iron Oxide

What is Molecular Structrure of Fe₃O₄?

The molecular structure of Fe3O4 is cubic inverse spinel

What is Magnetic Nature of Fe₃O₄?

Fe₃O₄ is Ferrimagnetic in Nature

Is Fe₂O₃ and Fe₃O₄ same?

No, Fe₂O₃ and Fe3O4 are not same. Fe₂O₃ is Iron(III) Oxide in which oxidation state of Iron is +3 whereas Fe₃O₄ is Iron (II, III) Oxide which is formed due to combination of FeO and Fe₂O₃

Is Fe₃O₄ called Rust?

No, Fe₃O₄ is not specifically rust. Rust is given by the formula Fe₂O₃.XH₂O