Question

\(\mathrm{NaOH}\) is prepared by the method: (a) Castner cell (b) Down's cell (c) Castner Kellner cell (d)Solvay process

Short answer

Sodium hydroxide is prepared using the Castner Kellner cell (option c).

Step-by-step solution

Understand the Methods Listed

First, let's understand what each method refers to: **Castner cell** is used for the production of alkali metals, particularly sodium. **Down's cell** is used for the electrolysis of molten sodium chloride to get pure sodium and chlorine. **Castner Kellner cell** is used for the production of sodium hydroxide via electrolysis of brine (saturated NaCl solution). The **Solvay process** is used to manufacture sodium carbonate, not sodium hydroxide.

Determine the Process for NaOH Production

Sodium hydroxide (NaOH) is commonly produced in industry through the electrolysis of brine, which involves an electrolyte that is a saturated solution of sodium chloride (NaCl). This process fits the description of the Castner Kellner cell where electricity is used to decompose the brine to produce chlorine gas at the anode, hydrogen gas at the cathode, leaving behind NaOH in solution.

Identify the Correct Answer

By recognizing the method used to produce NaOH and having identified which cell is responsible, we match the method to its options. From the available choices: Castner cell, Down's cell, Castner Kellner cell, and Solvay process, only the **Castner Kellner cell** (option (c)) fits the description of producing NaOH.

Key concepts

Electrolysis of Brine

The electrolysis of brine is a fundamental chemical process where a saturated solution of sodium chloride (NaCl), commonly known as table salt, is decomposed using electrical energy. Through electrolysis, the compound is broken down into different substances. This specific process is utilized in the production of sodium hydroxide (NaOH), chlorine (Cl₂), and hydrogen (H₂) gases.

Here's essentially how it works:

• The brine solution acts as the electrolyte, conducting electricity between the positive electrode (anode) and the negative electrode (cathode).
• At the anode, chloride ions are oxidized to produce chlorine gas.
• At the cathode, hydrogen ions from the water are reduced to produce hydrogen gas.
• Sodium ions and hydroxide ions remain behind in the solution, forming sodium hydroxide.

This process is significant because it helps produce chemicals that are crucial for various industries, from cleaning products to pharmaceuticals.

It is important to note that controlling the conditions of this process, such as temperature and concentration, is critical to ensure the purity and efficiency of the products obtained.

Castner Kellner Cell

The Castner Kellner cell is a specialized device used industrially for the production of sodium hydroxide through the electrolysis of brine. In terms of structure, the cell is divided into compartments to effectively separate and collect different components resulting from the electrolysis.

Let's explore its operation:

• The cell is designed with a diaphragm or a membrane to prevent the recombination of the produced chlorine with sodium hydroxide.
• The central compartment houses the brine solution, while the outer parts allow the operative pathways to isolate sodium ions and generate chlorine gas.
• Chlorine is collected at the anode compartment, and hydrogen is collected at the cathode compartment.
• Simultaneously, sodium hydroxide is formed in the central compartment.

The Castner Kellner cell is important because it enables the efficient production of both chlorine and sodium hydroxide in large quantities, ensuring that economic and industrial demands are met effectively. It's a more sustainable way to use raw materials with minimal waste.

Industrial Chemistry

Industrial chemistry refers to the large-scale production of chemical products and materials that are used in everyday life. It plays a crucial role in converting chemical reactions into scalable processes to satisfy industrial demands efficiently.

In the realm of industrial chemistry, the production of sodium hydroxide via the electrolysis of brine is a perfect example. Sodium hydroxide is a vital industrial chemical, utilized in various sectors, such as:

• Manufacturing: used in the production of paper, textiles, and soap.
• Chemical Reactions: acts as a pH regulator and a reagent for various chemical syntheses.
• Environmental: employed for water treatment and refining petroleum.

The industry relies on techniques like those in the Castner Kellner cell to produce the substantial quantities required.

Industrial chemistry continuously strives for more efficient, cost-effective, and greener processes. Thus, improvements in technology and infrastructure are constantly pursued to meet the evolving demands and environmental regulations.