Problem 120 - A Complete Resource Book in Chemistry for JEE Main

Question

An insecticide SEVIN is made by the reaction of 1 - naphthol with methyl isocyanate. A union carbide plant in Bhopal, India, were using this process to make SEVIN for use as an agricultural insecticide. On December 3,1984 , either by accident or by sabotage, a value was opened that admitted water to a large tank of methyl isocyanate. The pressure and temperature within the tank rose very high and the pressure relief value opened to prevent the tank from bursting. A large quantity of methyl isocyanate rushed through the pressure relief valves and the vapours flowed with the breeze into populated areas, killing about 2500 people and injuring many more. The pressure rise in the container (tank) was due to liberation of (a) \(\mathrm{CH}_{4}\) (b) \(\mathrm{NH}_{3}\) (c) \(\mathrm{CO}\) (d) \(\mathrm{CO}_{2}\)

Step-by-Step Solution

Answer

(d) \( \mathrm{CO}_{2} \)

Step 1: Understanding the Problem

The problem asks us to determine which gas was released in the reaction that caused the pressure increase in the tank of methyl isocyanate. This problem is about identifying the by-product of a chemical reaction.

Step 2: Chemical Reaction Analysis

When methyl isocyanate ( ext{MIC}) comes in contact with water, it undergoes a chemical reaction. This reaction is known to produce methylamine, carbon dioxide ( ext{CO}_2), and heat, leading to increased pressure.

Step 3: Identifying the Gas

The key component responsible for the pressure rise is the generation of a gas. As the reaction between methyl isocyanate and water produces carbon dioxide ( ext{CO}_2), this is the gas responsible for the increase in pressure.

Key Concepts

Methyl Isocyanate Reaction

Methyl isocyanate (MIC) is a highly reactive compound that is used in the production of certain pesticides, including the pesticide Sevin. It is particularly volatile, meaning it can easily vaporize and become a gas. When MIC comes into contact with water, it reacts to produce several compounds, including carbon dioxide (CO₂) and methylamine. This reaction releases a significant amount of heat, which further escalates the situation by increasing the temperature inside any container where this reaction occurs. This increase in temperature leads to an increase in pressure, particularly if the container is sealed, as gases expand when heated. So, the main products of the reaction between methyl isocyanate and water include:

• Methylamine
• Carbon dioxide (CO₂)
• Heat, which causes an increase in pressure

Understanding these products allows one to see why the pressure in the Bhopal incident rose so dangerously high.

Bhopal Gas Tragedy

On the night of December 2-3, 1984, a catastrophic event unfolded in Bhopal, India. This tragedy revolved around a Union Carbide pesticide plant where methyl isocyanate (MIC) was used in production processes. Unfortunately, a failure or possible sabotage led to water entering a storage tank filled with MIC. This accidental mixing caused the reaction between MIC and water, resulting in the rapid generation of carbon dioxide gas and heat. As pressure built up inside the tank, safety valves released these gases into the air. The reaction also caused the liberation of MIC vapors. The result was a massive gas leak that drifted over densely populated areas, leading to widespread casualties. It was one of the most devastating industrial accidents in history:

• Thousands were killed directly by the toxic effects of the gases.
• Tens of thousands suffered from various injuries and long-term health effects.

The Bhopal disaster is a somber reminder of the necessity of stringent safety measures when handling hazardous chemicals.

Chemical Reaction By-products

Understanding chemical reactions involves knowing what by-products are produced and how they impact the environment. In the context of industrial accidents, the by-products can turn a manageable situation into a catastrophe. In the case of the Bhopal incident, when water mixed with methyl isocyanate (MIC), several by-products were generated. Carbon dioxide (CO₂) was the main gaseous by-product that contributed to the pressure build-up inside the tank. However, this was not the only concern; the chemical reaction also produced other hazardous substances that added to the toxic nature of the gas leak. Key by-products from the MIC reaction include:

• Carbon dioxide, which increased pressure inside the storage tank.
• Methylamine, another toxic substance but less prominent in the immediate aftermath.
• Additional heat, contributing to the rapid expansion of gases.

Recognizing the potential by-products and their properties is crucial in preventing similar accidents in chemical industries in the future.