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

Question

In the Castner's process of extraction of sodium cathode is (a) nickel rod (b) iron rod (c) graphite rod (d) copper rod

Step-by-Step Solution

Answer

The cathode in Castner's process is a graphite rod (c).

Step 1: Understanding the Problem

The problem asks about the type of rod used as the cathode material in the Castner's process of extracting sodium. Understanding the function and material compatibility is key to solving this.

Step 2: Reviewing Castner's Process

Castner's process is an electrolytic process used to extract sodium. In this process, a suitable material should be chosen for the cathode that withstands the environment and reactions occurring during electrolysis.

Step 3: Identifying Suitable Cathode Material

The cathode needs to be resistant to corrosion and able to conduct electricity efficiently. Among the options, graphite is known for its stable and conductive properties in electrolytic processes.

Step 4: Choosing the Correct Option

Given the requirements for a cathode in Castner's process, the correct choice of material among the options provided is graphite. Therefore, the cathode in Castner's process of sodium extraction is a graphite rod.

Key Concepts

Electrolytic Extraction of Sodium

The electrolytic extraction of sodium is a key component of the Castner's process. This process involves using electricity to drive a chemical reaction, which separates sodium from its compounds. In the case of Castner's process, sodium chloride or sodium hydroxide is typically used as the source of sodium. By passing an electric current through the molten mixture, sodium ions are converted into sodium metal at the cathode, while chloride or hydroxide ions are converted into gas at the anode.
This separation technique is favored for its efficiency and the purity of the sodium it produces. The whole process hinges on the appropriate setup of electrodes, which are crucial for maintaining the right conditions for electrolysis.

• Starts with a sodium compound, often sodium chloride.
• Electrolysis is conducted in a specialized cell.
• Separation of sodium occurs through an electric charge.
• Process must control temperature and electrolyte composition.

The Castner's process is both industrially viable and cost-effective, making it an important method in the production of sodium.

Cathode Material

The choice of cathode material in any electrolytic process is crucial since it must withstand the conditions of the electrochemical reaction. In Castner's process, the cathode must not only conduct electricity well but also resist corrosion from the molten electrolyte environment. This is why selecting the right material is so important.
A good cathode material needs to have:

• High conductivity to efficiently transfer electrons.
• Resistance to degradation and corrosion.
• A cost-effective price for industrial production.

Among available materials like nickel, iron, and copper, graphite stands out because it provides all these qualities. Its ability to withstand high temperatures and chemical reactions without degrading makes it the ideal choice for the cathode in the Castner's process.

Graphite Rod

Graphite rods are often chosen as the cathode material in the Castner's process thanks to their exceptional properties. Graphite is a form of carbon that is an outstanding conductor of electricity, which makes it perfect for its role in electrolysis. Moreover, it is chemically inert and highly resistant to thermal shock, ensuring it does not react with the substances in the electrolytic cell.
These rods are employed in a variety of electrochemical applications, not just sodium extraction. Graphite's physical properties allow it to maintain integrity under the intense heat and harsh chemical environment inherent in processes like these. Additional advantages of using graphite rods include:

• Low cost, despite its excellent properties.
• Ease of fabrication into various sizes and shapes.
• Low reactivity allows long operational life.

By using graphite rods, the Castner's process maintains efficiency and reliability in sodium production, making graphite an invaluable material in industrial electrolysis operations.