Problem 3 - A Complete Resource Book in Chemistry for JEE Main

Question

Carbon black, which is used in making printer's ink is obtained by the decomposition of (a) acetylene (b) benzene (c) carbon tetrahedral (d) methane

Step-by-Step Solution

Answer

Acetylene is decomposed to make carbon black.

Step 1: Identify the Problem

We need to determine which compound is decomposed to obtain carbon black, used in making printer's ink. The options given are acetylene, benzene, carbon tetrahedral, and methane.

Step 2: Understand the Decomposition Process

Carbon black is produced by the incomplete combustion or thermal decomposition of hydrocarbons. In this context, we need to identify which of the given substances is commonly known to be decomposed for producing carbon black.

Step 3: Analyze Each Option

Let's analyze the given compounds: (a) Acetylene - Known for producing carbon black through incomplete combustion. (b) Benzene - Typically not used for producing carbon black. (c) Carbon tetrahedral - This is likely a typo; it might mean carbon tetrachloride, which is not used for carbon black. (d) Methane - It is used to produce carbon black, but acetylene is more specifically used.

Step 4: Choose the Most Suitable Answer

Considering the chemical industry standards and processes, acetylene (option a) is most commonly used for the production of carbon black through decomposition.

Key Concepts

Incomplete Combustion

Incomplete combustion is a process where a fuel burns in insufficient oxygen, not allowing it to turn fully into carbon dioxide and water. Instead, this process often results in byproducts such as carbon monoxide, soot, or carbon black.
When applied to producing carbon black, incomplete combustion involves burning a hydrocarbon, like acetylene, under controlled conditions where oxygen is limited. This limited oxygen supply prevents the complete conversion of acetylene into carbon dioxide. As a result, the leftover carbon forms as carbon black, a fine powdery substance.
The primary ways incomplete combustion occurs are:

• Limited oxygen availability
• Low combustion temperature
• Incomplete mixing of fuel and air

These conditions are precisely managed in industrial processes to maximize the production of carbon black.

Acetylene Decomposition

Acetylene, a simple hydrocarbon with the formula \(C_2H_2\), is an ideal candidate for carbon black production due to its high carbon content.
The thermal decomposition of acetylene is a widely utilized method in the chemical industry for producing carbon black. In this method, acetylene is heated to high temperatures, typically in the absence of air, causing the molecule to break down into its elemental components.
Acetylene decomposition is characterized by its efficiency in yielding a high percentage of carbon black with minimal impurities. This process proceeds by:

• Heating acetylene to temperatures above 800°C
• Conducting the reaction in a closed system devoid of oxygen
• Collecting the carbon black as it forms as tiny, sticky particles of soot

The efficiency and quality of the carbon black produced are crucial for applications such as printer's ink and other industrial uses.

Chemical Industry Standards

In the chemical industry, various standards regulate the production processes to ensure safety, efficiency, and quality control. In the context of carbon black production, the industry follows certain standards to achieve the desired product quality and ensure worker safety.
Key standards in carbon black production include:

• Ensuring precise control of the combustion process to achieve a high yield
• Maintaining appropriate temperature and oxygen levels to prevent contamination
• Implementing thorough safety measures to handle the gases and heat involved safely

These standards also mandate the extensive testing of the carbon black produced, to ensure it meets the necessary specifications for its intended use. Following these stringent guidelines helps industries globally to produce high-quality carbon black efficiently and safely, suitable for various applications from inks to tire manufacturing.