Question

In the Castner's process of extraction of sodium cathode is: (a) Nickel rod (b) Iron rod (c) Graphite rod (d) Copper rod

Short answer

The cathode in Castner's process is a Nickel rod.

Step-by-step solution

Understand Castner's Process

Castner's process is used for the electrolytic extraction of sodium. It involves the electrolysis of molten sodium hydroxide. The key components of any electrolytic cell are the anode and the cathode. It's important to identify what material is used as the cathode in this specific process.

Analyze Cathode Material

In Castner's process, we need a material for the cathode that does not react with sodium while the electrolysis takes place. The options given are nickel rod, iron rod, graphite rod, and copper rod. Traditionally, a nickel rod is employed since it is inert and can conduct electricity effectively, without reacting with sodium.

Select the Correct Answer

Based on the analysis in the previous step, the cathode in the Castner's process is typically made from nickel. This is to ensure that the cathode can withstand the conditions of the electrolytic cell and does not react with the sodium being extracted.

Key concepts

Electrolytic Extraction

Electrolytic extraction is a fundamental process in chemistry used to extract metals from their compounds by means of electricity. In this process, an electric current is passed through a molten or dissolved compound, leading to the movement of ions that results in the separation of metals from non-metals. Castner's process is one such method used primarily for the extraction of sodium. By leveraging the principles of electrolysis, this process allows the metallic sodium to be deposited in a pure form. It is important to note that the success of electrolytic extraction depends greatly on the setup of the electrolytic cell. This includes both the anode and cathode materials, which play crucial roles in the overall chemical reactions taking place within the cell.

Sodium Hydroxide Electrolysis

The electrolysis of sodium hydroxide is a crucial step in the Castner's process. Here, molten sodium hydroxide (NaOH) is used as the electrolyte. During electrolysis, the sodium ions (Na⁺) migrate towards the cathode, where they gain electrons and are deposited as solid sodium metal. Meanwhile, the hydroxide ions (OH⁻) move towards the anode where they discharge oxygen gas. The reaction at the cathode can be represented as:

• Cathode: Na⁺ + e⁻ → Na

And at the anode:

• Anode: 4OH⁻ → 2H₂O + O₂ + 4e⁻

This process not only produces sodium metal but also releases oxygen gas as a byproduct. It's a highly efficient method given that the appropriate conditions, such as the right temperature and pure electrolyte, are maintained. The choice of cathode material further influences the efficiency and purity of the extracted sodium.

Cathode Material Selection

In any electrolysis process, selecting the right cathode material is crucial. It affects both the efficiency of the electrolysis and the purity of the result. For Castner's process, the choice of cathode material must ensure that it does not react with sodium metal or deteriorate over time. Various materials can serve as cathodes, but factors like conductivity, chemical inertness, and mechanical stability must be considered. The materials under consideration in Castner's process include nickel, iron, graphite, and copper. Nickel is typically preferred because it offers the necessary conductivity and is chemically inert, preventing any unwanted reactions during the sodium extraction. The ideal cathode material prevents contamination of the extracted metal, ensuring a high-quality yield.

Nickel Rod as Cathode

Nickel is often selected as the cathode material in Castner's process. This choice is due to several favorable properties that nickel possesses as a cathodic material. - **Inertness:** Nickel is relatively inert, meaning it doesn't easily react with sodium, which maintains the purity of the extracted metal. - **Conductivity:** It offers good electrical conductivity, allowing efficient electron flow during electrolysis. - **Durability:** Nickel can withstand the high temperatures and corrosive environment present during the electrolysis of sodium hydroxide. These characteristics make the nickel rod an excellent choice for use as a cathode. It ensures operational efficiency while maintaining the structural integrity of the electrolytic cell over prolonged periods of operation. Thus, for sodium extraction in the Castner's process, a nickel rod stands out as a superior option compared to other potential materials.