Problem 76 - A Complete Resource Book in Chemistry for JEE Main

Question

Which one of the following is used in the industrial preparation of nitric acid by Ostwald's process? (a) \(\mathrm{NH}_{3}\) (b) \(\mathrm{N}_{2} \mathrm{O}_{5}\) (c) \(\mathrm{NH}_{4} \mathrm{NO}_{3}\) (d) \(\mathrm{N}_{2}\)

Step-by-Step Solution

Answer

The correct option is (a) \(\mathrm{NH}_{3}\).

Step 1: Understand Ostwald's Process

The Ostwald process is an industrial method used for producing nitric acid. The process involves the oxidation of ammonia (\(\mathrm{NH}_3\)) to form nitric acid.

Step 2: Identify the Reactant

In the Ostwald process, the primary reactant used is ammonia (\(\mathrm{NH}_3\)). This ammonia is oxidized in a series of reactions to eventually produce nitric acid.

Step 3: Analyze the Options

We need to select the compound used in the industrial preparation from the given options: - (a) \(\mathrm{NH}_{3}\) - (b) \(\mathrm{N}_{2} \mathrm{O}_{5}\) - (c) \(\mathrm{NH}_{4} \mathrm{NO}_{3}\) - (d) \(\mathrm{N}_{2}\). Only \(\mathrm{NH}_{3}\) fits the role as the starting material in the Ostwald process.

Key Concepts

Nitric Acid Production

Nitric acid is a vital industrial chemical used in fertilizers, explosives, and many other products. One of the most common methods of producing this versatile acid is the Ostwald process. The main goal of this process is to transform ammonia (\(\mathrm{NH}_3\)) into nitric acid through a carefully controlled set of chemical reactions. This method is efficient and suitable for large-scale production, making it ideal for industrial use.

The process begins with ammonia, which is obtained from natural gas or produced through the Haber-Bosch process. In the presence of heat and a catalyst, such as platinum, ammonia reacts with oxygen from the air. This step generates nitrogen monoxide (\(\mathrm{NO}\)), a crucial intermediate that continues to react further. Ultimately, the sequence of reactions leads to the formation of nitric acid (\(\mathrm{HNO}_3\)).

Understanding the role of each chemical in this process is vital, as it illuminates the complex choreography that turns basic starting materials into valuable nitric acid used worldwide.

Oxidation of Ammonia

The oxidation of ammonia (\(\mathrm{NH}_3\)) is the cornerstone of the Ostwald process. This reaction forms the foundation upon which nitric acid production is built. During this step, ammonia combines with oxygen to produce nitrogen monoxide (\(\mathrm{NO}\)) and water. The reaction can be represented by the balanced equation:\[4\mathrm{NH}_3 + 5\mathrm{O}_2 \rightarrow 4\mathrm{NO} + 6\mathrm{H}_2\mathrm{O}\]

Catalysts play a significant role in making this process efficient. Platinum, often supported by rhodium, is typically used to speed up the reaction without being consumed. The heat involved and the choice of the catalyst are crucial factors that ensure maximum yield of the desired products.

Subsequent to the formation of nitrogen monoxide, the molecule reacts further with more oxygen. This reaction produces nitrogen dioxide (\(\mathrm{NO}_2\)), which is pivotal in the nitric acid manufacturing process. The value of ammonia's oxidation lies in its ability to easily transform into key nitrogen oxides that further react to generate the desired nitric acid.

Industrial Preparation of Nitric Acid

The industrial preparation of nitric acid is an intricate process that primarily uses the Ostwald process. Focusing on efficiency and yield, this method has been refined over time since its invention by Wilhelm Ostwald in 1902. The principle behind its industrial application is its ability to convert simple starting material - ammonia - into nitric acid through a series of controlled, exothermic reactions.

In industrial settings, key considerations include the choice of catalyst, the management of reaction conditions like temperature and pressure, and the recovery and recycling of unreacted gases.

• Initial oxidation of ammonia into nitrogen monoxide.
• Further oxidation of nitrogen monoxide into nitrogen dioxide.
• Hydrolysis and absorption of nitrogen dioxide in water, forming nitric acid.

Commercial plants carefully design these steps to maximize productivity while minimizing waste, ensuring maximum economic and environmental benefits. The ammonia used is typically derived from the Haber-Bosch process, linking two major industrial chemical processes synergistically. This interconnection highlights the sophistication and efficiency of modern chemical manufacturing systems, providing vital components needed globally.