Problem 33 - A Complete Resource Book in Chemistry for JEE Main

Question

\(\mathrm{N}_{2}(\mathrm{~g})+3 \mathrm{H}_{2}(\mathrm{~g})=\frac{\mathrm{Fe} / \mathrm{Mo}, 500^{\circ} \mathrm{C}}{\mathrm{V} 200-900 \mathrm{~atm}} 2 \mathrm{NH}_{3}+22.4\) \(\mathrm{kcal}\) formation of \(\mathrm{NH}_{3}\) by above reaction shows (a) Cyanamide process (b) Serpeck's process (c) Haber process (d) None of these

Step-by-Step Solution

Answer

The formation of \( \mathrm{NH}_{3} \) by the above reaction is based on the Haber process.

Step 1: Identify the Reaction

Examine the given chemical reaction: \( \mathrm{N}_{2}(\mathrm{~g}) + 3 \mathrm{H}_{2}(\mathrm{~g}) \rightarrow 2 \mathrm{NH}_{3} \). The reaction involves the synthesis of ammonia \( \mathrm{NH}_{3} \) from nitrogen and hydrogen gases.

Step 2: Analyze the Reaction Conditions

The reaction occurs at high pressure (200-900 atm) and elevated temperature (about 500°C), utilizing an iron-molybdenum (Fe/Mo) catalyst. This is mentioned as 'Fe/Mo, 500°C / V 200-900 atm' in the equation.

Step 3: Compare with Known Industrial Processes

The conditions—high pressure, high temperature, and an iron catalyst—are characteristic of the Haber process. The Haber process is well-known for ammonia synthesis, involving nitrogen and hydrogen under these conditions.

Step 4: Match with Given Choices

The problem provides four options: (a) Cyanamide process, (b) Serpeck's process, (c) Haber process, and (d) None of these. Based on analysis, the reaction aligns with the Haber process.

Key Concepts

Ammonia synthesis

Ammonia synthesis is a fundamental chemical process that involves converting nitrogen (N_2(g)) and hydrogen (H_2(g)) gases into ammonia (NH_3). This transformation is key in the production of fertilizers, which are crucial for modern agriculture. The chemical equation for this synthesis is typically written as: \[ \mathrm{N}_{2} + 3 \mathrm{H}_{2} \rightarrow 2 \mathrm{NH}_{3} \] This reaction not only plays a significant role in feeding the world's population by providing essential nutrients to plants, but it also exemplifies industrial chemistry's developments in scaling up laboratory processes for large-scale production.

• Ammonia is a colorless gas with a pungent odor.
• It is significantly used in agriculture, chemicals, and even pharmaceuticals.
• The reaction is exothermic, releasing about 22.4 kcal/mol of energy.

Understanding the ammonia synthesis process helps in grasping how vital raw materials like nitrogen and hydrogen are transformed under specific conditions into products essential for human survival.

Industrial chemistry

Industrial chemistry refers to the large-scale chemical processes that transform raw materials into useful products, essential for various aspects of daily life. In the context of ammonia synthesis, industrial chemistry involves optimizing reaction conditions—such as temperature, pressure, and catalyst choice—to efficiently produce ammonia for industrial uses. The Haber process underscores this field, showcasing how fundamental chemical reactions can be adapted for mass production. This process is not just a triumph of scientific discovery, but also of engineering, as it requires formidable conditions to ensure significant yield:

• High pressure (200-900 atm) to improve reaction rates and yield.
• Elevated temperatures (around 500°C) for kinetic favorability.
• Use of catalysts to lower energy barriers.

By converting the laboratory synthesis of ammonia into an essential industrial operation, the Haber process marks a cornerstone of industrial chemistry. It enables the synthesis of a vital compound, aiding considerably in global agriculture and food production.

Catalyst

A catalyst is a substance that accelerates a chemical reaction without undergoing any permanent change itself. In the Haber process, the choice of catalyst is crucial to enhance the reaction between nitrogen and hydrogen gases to form ammonia. The commonly used catalyst here is iron ( Fe ), often enhanced with small amounts of molybdenum ( Mo ), to improve its effectiveness and durability. Here's why a catalyst is indispensable in ammonia synthesis:

• Reduces activation energy, allowing the reaction to proceed more quickly at a given temperature.
• Increases the rate of production, making the process economically viable.
• Remains unchanged, providing continuous catalytic effect throughout the process.

Catalysts enable the Haber process to function under industrial conditions by facilitating higher reaction rates without the need for excessively high temperatures, which could compromise equipment and safety. Hence, the choice of catalyst is fundamental to the efficiency and feasibility of ammonia production.