Problem 160 - A Complete Resource Book in Chemistry for JEE Main

Question

Match the following (a) Castner Kellner (p) \(\mathrm{MgCl}_{2} .5 \mathrm{MgO} \cdot \mathrm{xH}_{2} \mathrm{O}\) cell (b) Pearl ash (q) \(\mathrm{K}_{2} \mathrm{CO}_{3}\) (c) Solvay's process (r) Manufacture of \(\mathrm{NaHCO}_{3}\)

Step-by-Step Solution

Answer

(a) Matches not provided, (b) q, (c) r

Step 1: Identify Castner Kellner

The Castner Kellner process is used for the electrochemical production of sodium and chlorine by electrolysis of molten sodium chloride. It is not directly related to the compounds or cells listed here. The answer is not available within the provided options.

Step 2: Identify Pearl Ash

Pearl ash is another name for potassium carbonate. Thus, the correct match for Pearl ash is \( \mathrm{K}_{2} \mathrm{CO}_{3} \).

Step 3: Identify Solvay's Process

The Solvay process is an industrial process widely used to produce sodium bicarbonate (\( \mathrm{NaHCO}_{3} \)) from sodium chloride and calcium carbonate. Therefore, it matches with the manufacture of \( \mathrm{NaHCO}_{3} \).

Key Concepts

The Castner Kellner Process

The Castner Kellner process is a fascinating method integral to industrial chemistry, particularly known for producing valuable chemicals like sodium and chlorine. This process uses electrolysis, which involves passing an electric current through molten sodium chloride (table salt) to trigger a chemical change.
Here's how it works: the molten salt, when subjected to an electrical current, splits into sodium and chlorine gas. Chlorine gas is released at the anode, while molten sodium is collected at the cathode.
This method is crucial in the industry due to its efficiency:

• It produces pure sodium, a highly reactive metal with numerous applications, including the manufacture of soaps, alkoxides, and other chemicals.
• It also yields chlorine, vital for producing hydrochloric acid, PVC, and disinfection products.

Despite its importance, the process requires careful control of conditions to ensure safety and efficiency. By understanding the electrolysis of sodium chloride, students can appreciate the elegant simplicity and power of industrial processes used in everyday products.

Understanding Pearl Ash

Pearl ash is essentially potassium carbonate, denoted as \( \mathrm{K}_{2} \mathrm{CO}_{3} \). Historically used in glass making and soap production, it's a crucial compound in chemistry. The name "pearl ash" originates from its production method, where potash was purified to obtain this white, pearly substance.
Potassium carbonate is valued for several reasons:

• It's a strong alkaline, which makes it effective in neutralizing acids.
• It acts as a drying agent due to its hygroscopic nature, meaning it absorbs moisture from the air.
• In baking, pearl ash is sometimes used as a leavening agent to make bread and cakes rise.

Today, its primary uses involve the manufacturing of glass, soap, and fertilizers. Understanding pearl ash not only ties back to historical chemical practices but also highlights the ongoing relevance of traditional compounds in modern-day applications.

The Solvay Process Unveiled

The Solvay process stands out in industrial chemistry for its ingenious approach to producing sodium bicarbonate, \( \mathrm{NaHCO}_{3} \), commonly known as baking soda. Developed in the 1860s by Ernest Solvay, this method revolutionized the way we obtain sodium bicarbonate from simple and abundant materials like sodium chloride (salt) and calcium carbonate (limestone).
The process involves these key steps:

• An ammonia-saturated brine solution reacts with carbon dioxide to produce ammonium bicarbonate.
• Ammonium bicarbonate reacts with sodium chloride to form sodium bicarbonate and ammonium chloride.
• The sodium bicarbonate precipitates out due to its low solubility and is then heated to form the desired sodium carbonate.

This method is not only efficient but also environmentally friendlier compared to older processes, as it recycles ammonia within the system. The widespread use of the Solvay process illustrates the power of clever chemical reactions to meet the demands of modern industry through sustainable practices.