Problem 30 - Advanced Problems in Physical Chemistry for Competitive Examinations

Question

In the Ostwald's process for the manufacture of \(\mathrm{HNO}_{3}\), the catalyst used is (a) \(\mathrm{Fe}\) (b) \(\mathrm{Pt}\) (c) \(\mathrm{V}_{2} \mathrm{O}_{5}\) (d) Mo

Step-by-Step Solution

Answer

(c) V_{2}O_{5}

Step 1: Identify the Ostwald Process Catalyst

The Ostwald process is used in the industrial production of nitric acid from ammonia. This process includes the oxidation of ammonia to nitrogen monoxide using a catalyst.

Step 2: Recall Known Catalysts for the Ostwald Process

The common catalyst used in the Ostwald process is Platinum (Pt) or alternatively, a vanadium(V) oxide (V2O5) catalyst is used.

Step 3: Select the Correct Answer

Since the process can use Platinum or vanadium(V) oxide, but Platinum is not listed as an option, the correct answer is (c) V2O5, as it is known to be used in this process.

Key Concepts

Catalyst in Nitric Acid Production

Understanding the role of a catalyst in the production of nitric acid via the Ostwald process is vital for students studying industrial chemistry. In simple terms, a catalyst is a substance that speeds up a chemical reaction without being consumed by the reaction itself. In the context of the Ostwald process, the catalyst is responsible for facilitating the rapid oxidation of ammonia (NH3) into nitrogen monoxide (NO).

While platinum (Pt) is an effective catalyst, its high cost often leads to the preference for vanadium(V) oxide (V2O5) in industrial applications. This substitution is advantageous due to vanadium(V) oxide's availability and cost-effectiveness, while still maintaining a high level of efficiency in the reaction. When exposed to the reaction conditions, V2O5 enables the oxidation of ammonia at relatively lower temperatures than would be possible without a catalyst, thereby saving energy and increasing the overall efficiency of the process.

Industrial Production of HNO3

The industrial synthesis of nitric acid, HNO3, is a cornerstone of the chemical industry and is fundamental in the production of fertilizers, explosives, and many other chemicals. The Ostwald process is the primary method used for producing nitric acid on a large scale.

It involves several steps, beginning with the catalytic oxidation of ammonia. This reaction produces nitrogen monoxide and water. Subsequently, the nitrogen monoxide reacts with oxygen to form nitrogen dioxide (NO2), which is further absorbed in water to yield nitric acid.

• The process is carefully controlled and requires specific conditions of temperature and pressure.
• The availability of high-purity ammonia and the efficient conversion of the reactants to the desired product are crucial for the profitability of the process.

Ensuring proper handling and maintenance of the catalysts involved is also imperative to sustain continuous production. The synthesized nitric acid can be concentrated and purified through distillation to meet various industrial requirements.

Oxidation of Ammonia

The starting point of the Ostwald process is the oxidation of ammonia, an exothermic reaction that lays the groundwork for creating nitric acid. To understand this better, let's look at the chemical equation: \[4NH_3(g) + 5O_2(g) \rightarrow 4NO(g) + 6H_2O(g)\] This reaction occurs in the presence of the catalyst, vanadium(V) oxide (V2O5), at temperatures around 400 - 450°C. The presence of the catalyst not only makes the reaction feasible at these temperatures compared to the much higher temperatures required without one but also ensures the reaction is selective towards the production of NO rather than other potential nitrogen oxides.

Importance of Reaction Conditions

The efficiency of ammonia oxidation is highly sensitive to the reaction conditions. Any deviation from the optimal temperature and pressure can lead to lower yields or the creation of undesirable byproducts. As a result, monitoring and controlling the process parameters are essential for maintaining an optimal output.