Problem 49 - A Complete Resource Book in Chemistry for JEE Main

Question

Which of the following is a ferrite? (a) \(\mathrm{MgFe}_{2} \mathrm{O}_{4}\) (b) \(\mathrm{Zn}_{3} \mathrm{FeO}_{4}\) (c) \(\mathrm{AlFe}_{2} \mathrm{O}_{4}\) (d) \(\mathrm{Na}_{2} \mathrm{Fe}_{2} \mathrm{O}_{4}\)

Step-by-Step Solution

Answer

(a) \( \mathrm{MgFe}_2 \mathrm{O}_4 \) is a ferrite.

Step 1: Understanding Ferrites

Ferrites are ceramic compounds consisting of iron oxide ( Fe_2O_3) combined chemically with one or more additional metallic elements. They generally have a chemical formula of the type MFe_2O_4, where M is a bivalent metal ion such as Mg, Zn, Ni, or Fe.

Step 2: Analyze Each Option

Review each chemical formula to determine if it matches the template for ferrites, MFe_2O_4. (a) MgFe_2O_4: Matches the template as M is Mg. (b) Zn_3FeO_4: Does not match the template. Zn should be only one. (c) AlFe_2O_4: Matches the template as M is Al. (d) Na_2Fe_2O_4: Does not match the template as it has two Na and two Fe atoms.

Step 3: Identify Correct Ferrite

From Step 2, the only options that match the ferrite formula template are (a) MgFe_2O_4 and (c) AlFe_2O_4. However, considering the types of ions commonly forming ferrites, Al is usually not considered as it typically doesn’t form bivalent ions like a ferrite requires. Therefore, MgFe_2O_4 is the correct ferrite.

Key Concepts

Chemical formula

A chemical formula is used to represent a compound's composition using symbols for the elements and numbers indicating the ratio of atoms. In the context of ferrites, the chemical formula typically takes the form \( M ext{Fe}_2 ext{O}_4 \). This indicates the presence of a bivalent metal ion \( M \), two iron ions \( ext{Fe} \), and four oxygen ions \( ext{O} \).

The chemical formula is crucial because it provides an easy way to identify the type of compound and its possible applications. For instance:

• The \( ext{M} \) in \( M ext{Fe}_2 ext{O}_4 \) can be substituted with various bivalent metal ions to customize the ferrite's properties for different uses.
• The consistent presence of \( ext{Fe}_2 ext{O}_3 \) in the formula signifies the ferritic nature of these compounds.

Different elements in the chemical formula may alter its magnetic and conductive characteristics, which are important in many industrial applications.

Bivalent metal ions

Bivalent metal ions are metal ions with a +2 charge, meaning they have lost two electrons. These ions play an essential role in the formation of ferrites. Common bivalent ions that often form ferrites include magnesium (\( ext{Mg}^{2+} \)), zinc (\( ext{Zn}^{2+} \)), and nickel (\( ext{Ni}^{2+} \)).

The bivalent nature of these ions is critical for balancing the charge in the ferrite compound, ensuring stability and neutrality.

• Each bivalent ion can pair with the \( ext{Fe}_2 ext{O}_4 \) group to create a stable compound.
• The selection of different bivalent ions can change the magnetic properties of the ferrite, which is why particular ions are chosen for specific applications.

Bivalent ions contribute to the durability and the emerging properties of the ferrites. Their selection is particularly important in applications related to electronics and magnetics.

Iron oxide compounds

Iron oxide compounds are a type of chemical compound made up of iron and oxygen. They are represented by formulas such as \( ext{Fe}_2 ext{O}_3 \), commonly known as ferric oxide. In ferrites, iron oxide is a primary component that interacts with bivalent metal ions to form the compound.

These compounds are characterized by their magnetic properties and are used in many everyday applications because of their unique characteristics.

• Iron oxide compounds like \( ext{Fe}_2 ext{O}_3 \) provide the essential iron content needed for the magnetic properties of ferrites.
• They contribute to the hardness and resistance to corrosion, making ferrites useful in many technological applications, from hard disks to microwave devices.

Understanding the role of iron oxide compounds in ferrites helps appreciate the structural integrity and usefulness offered by these materials in various fields.