Problem 20 - A Complete Resource Book in Chemistry for JEE Main

Question

Moderate electrical conductivity is shown by (a) diamond (b) carborundum (c) graphite (d) silica

Step-by-Step Solution

Answer

Graphite (c) shows moderate electrical conductivity.

Step 1: Identify Conductive Properties

To solve this, first understand the properties of each material in terms of electrical conductivity. Diamond is an excellent insulator, carborundum is typically an insulator unless doped, graphite is a good electrical conductor, and silica is mainly an insulator normally.

Step 2: Select Based on Moderate Conductivity

Given the options and their conductive properties, graphite is known for having a good level of electrical conductivity due to its structure of layers that allow electrons to move freely. In contrast, the other options are primarily insulators.

Step 3: Conclude the Correct Choice

Since graphite is the only material here that naturally allows for moderate to high electrical conductivity, it stands out as the answer to the question about moderate electrical conductivity.

Key Concepts

Diamond Electrical Properties

Diamond is renowned for its exceptional hardness and sparkling beauty but not for electrical conductivity. It is an excellent insulator. This means it doesn't allow the free flow of electrons. The reason behind this lies in its atomic structure.

• Diamond is formed from carbon atoms arranged in a three-dimensional tetrahedral network.
• This robust and tight bond structure restricts the movement of electrons.
• All valence electrons are tied up in strong covalent bonds, leaving no room for free electrons to move about.

As a result, diamond's electrical properties make it suitable for applications where insulation is necessary.

Graphite Conductivity

Graphite stands out among carbon-based materials as being an excellent conductor of electricity. Its unique layered structure provides a much different functionality compared to diamond.

• Graphite is composed of layers of carbon atoms, each forming a planar hexagonal arrangement.
• The individual carbon atoms within these layers are bonded strongly, but the layers themselves are held together by weak Van der Waals forces.
• This allows the layers to slide over each other, promoting the movement of electrons across the layers.
• The presence of free-moving electrons in these planes gives graphite its high electrical conductivity.

Therefore, graphite is commonly used in applications where electrical conductivity is required, such as in batteries and as electrodes.

Insulators in Chemistry

In chemistry, insulators play a crucial role by preventing the passage of electrical current. Most materials classified as insulators have tightly bound electrons.

• Insulators like diamond and silica possess strong covalent bonds where electrons are not free to move.
• This absence of free electrons renders them incapable of transferring electrical energy.
• They are typically used in electrical equipment to provide safe pathways without electricity leaks.

Understanding the role of insulators helps in the development and safe usage of electronic devices.

Properties of Carborundum

Carborundum, also known as silicon carbide, is a compound of silicon and carbon with distinct properties.

• Normally, carborundum behaves as an insulator, making it less conductive under standard conditions.
• However, when doped with other elements, it can show semiconductor properties, enabling its use in various electronic applications.
• These doping processes introduce impurities that provide free charge carriers.

This unique ability to control conductivity through doping makes carborundum valuable in manufacturing electronic components such as LEDs and high-voltage devices.