Question

The industrial preparation of nitric acid by Ostwald's process involves (a) hydrolysis of \(\mathrm{NH}_{3}\) (b) reduction of \(\mathrm{NH}_{3}\) (c) hydrogenation of \(\mathrm{NH}_{3}\) (d) oxidation of \(\mathrm{NH}_{3}\)

Short answer

The answer is (d) oxidation of NH₃.

Step-by-step solution

Understanding the Ostwald Process

The Ostwald process is an industrial method used to produce nitric acid (HNO₃). It involves several chemical reactions primarily focused on the use of ammonia (NH₃) as the starting material. The key step in this process is the oxidation of ammonia, which leads to the formation of nitrogen oxides that are subsequently converted into nitric acid.

Identifying the Correct Reaction

To determine which option correctly describes the Ostwald process, consider the nature of the reactions involved. During the Ostwald process, ammonia (03NH₃03) is oxidized to form nitric oxide (03NO03), which then further reacts with oxygen to produce nitrogen dioxide (03NO₂03). These reactions focus on "oxidation" of ammonia.

Reviewing the Options

The options are: (a) hydrolysis of NH₃, (b) reduction of NH₃, (c) hydrogenation of NH₃, and (d) oxidation of NH₃. Based on the process we analyzed in Step 2, none of the processes involve hydrolysis or hydrogenation. Since the Ostwald process requires oxidation, the reduction is also incorrect.

Selecting the Correct Answer

From the analysis, option (d) 'oxidation of NH3' best describes the key chemical reaction in the Ostwald process. Thus, the correct answer to the question is option (d).

Key concepts

Oxidation of Ammonia

The oxidation of ammonia is the pivotal first step in the Ostwald process, a method for producing nitric acid (HNO₃) on an industrial scale. This chemical reaction involves converting ammonia (NH₃) into nitric oxide (NO), a compound crucial for further reactions in nitric acid production.

The process begins by mixing ammonia with a large amount of air. The mixture is then compressed and subsequently passed over a platinum catalyst at high temperatures, typically around 900°C.

• This catalyst is vital as it speeds up the reaction without being consumed in the process.
• During this reaction, ammonia is oxidized, which means its hydrogen atoms are replaced by oxygen, forming water as a byproduct.
• The overall chemical equation for this step is: \[4 \text{NH}_3 + 5 \text{O}_2 \rightarrow 4 \text{NO} + 6 \text{H}_2\text{O}\]

As a result, nitric oxide is produced, being the first and crucial compound in the chain of reactions leading to nitric acid. Understanding this oxidation step is essential, as it lays the groundwork for subsequent transformations in the Ostwald process.

Industrial Preparation of Nitric Acid

The industrial preparation of nitric acid hinges on the sequence of chemical reactions performed during the Ostwald process. After the initial oxidation of ammonia to nitric oxide, a series of transformations takes place to convert those nitrogen oxides into usable nitric acid.

Following oxidation, the formed nitric oxide (NO) reacts further with oxygen in the air to produce nitrogen dioxide (NO₂). This reaction occurs at a lower temperature compared to the initial ammonic oxidation.

• The chemical reaction for this step is given by: \[2 \text{NO} + \text{O}_2 \rightarrow 2 \text{NO}_2\]
• Nitrogen dioxide is an important intermediate in the production of nitric acid.
• The nitrogen dioxide (NO₂) is then absorbed in water, which leads to the formation of nitric acid (HNO₃).
• The water absorption can be represented as: \[3 \text{NO}_2 + \text{H}_2\text{O} \rightarrow 2 \text{HNO}_3 + \text{NO}\]

This stepwise conversion method makes the Ostwald process efficient and scalable for industrial needs. Understanding these transformations is crucial for appreciating how nitric acid is mass-produced.

Chemical Reactions in Nitric Acid Production

The Ostwald process is an intricate system where a sequence of chemical reactions converts simple ammonia into highly useful nitric acid. The heart of these reactions is the continuous oxidation and reduction processes, helping scientists and engineers to efficiently produce nitric acid on a large scale.

• The initial oxidation of ammonia results in the formation of nitric oxide, as previously explained.
• This is followed by further oxidation to get nitrogen dioxide, which will interact with water to produce nitric acid.
• Each of these steps involves carefully controlled conditions such as temperature, pressure, and the presence of a catalyst.
• A significant aspect of these reactions is their exothermic nature, meaning they release energy, which can be harnessed to drive the process further.
• Any excess nitric oxide produced during water absorption is recycled back into the system, enhancing efficiency and minimizing waste.

These chemical reactions showcase a fundamental interplay between chemistry and industrial processes, illustrating the importance of transforming simple reactions for broad industrial applications.