What is not a key step in the production of nitric acid by the Ostwald process? (a) \(\mathrm{N}_{2}(\mathrm{~g})+\mathrm{O}_{2}(\mathrm{~g}) \rightarrow 2 \mathrm{NO}(\mathrm{g})\) (b) \(3 \mathrm{NO}_{2}(\mathrm{~g})+\mathrm{H}_{2} \mathrm{O}(1) \rightarrow 2 \mathrm{HNO}_{3}\) (aq) \(+\mathrm{NO}(\mathrm{g})\) (c) \(4 \mathrm{NH}_{3}(\mathrm{~g})+5 \mathrm{O}_{2}(\mathrm{~g}) \rightarrow 4 \mathrm{NO}(\mathrm{g})+6 \mathrm{H}_{2} \mathrm{O}(1)\) (d) \(2 \mathrm{NO}(\mathrm{g})+\mathrm{O}_{2}(\mathrm{~g}) \rightarrow 2 \mathrm{NO}_{2}(\mathrm{~g})\)

The Ostwald process is a cornerstone in the industrial production of nitric acid, a chemical crucial for the manufacture of fertilizers, explosives, and many other chemical products. In simple terms, nitric acid is produced by the stepwise oxidation of ammonia (NH3). This process begins with ammonia reacting with oxygen to form nitric oxide (NO), which then combines with more oxygen to form nitrogen dioxide (NO2). This nitrogen dioxide is absorbed in water, which results in the formation of nitric acid (HNO3) and nitric oxide (NO), the latter of which is recycled back into the process.

Nitric acid production is an exemplary display of industrial chemistry, taking a common substance like ammonia and, through a series of controlled reactions and catalytic processes, converting it into a substance with a wide range of applications. The efficiency of this process has significant economic implications, as nitric acid is in high demand for various sectors. Understanding the individual steps and how they contribute to the overall efficiency of the process is crucial for students and professionals in the field alike.

A pivotal part of the Ostwald process is the catalytic oxidation of ammonia. It's the initial step where gaseous ammonia (NH3) is combined with oxygen (O2) in the presence of a catalyst—most commonly platinum or rhodium gauze—to form nitric oxide (NO) and water (H2O). Here's the balanced equation for the reaction:
\[4\text{NH}_3(\text{g}) + 5\text{O}_2(\text{g}) \rightarrow 4\text{NO}(\text{g}) + 6\text{H}_2\text{O}(l)\].

The catalyst is crucial as it lowers the activation energy required for the reaction, allowing it to occur at a lower temperature and at a faster rate. This not only conserves energy but also increases yield, making the process more cost-effective. The catalytic oxidation of ammonia is a practice that professionals must understand to optimize production and address any environmental concerns associated with the release of nitrogen oxides.

Nitrogen oxides, often referred to as NOx, play a vital role in the chemistry of the Ostwald process. The first oxide formed, nitric oxide (NO), is colorless but rapidly reacts with oxygen to form the reddish-brown nitrogen dioxide (NO2), as shown in the equation:
\[2\text{NO}(\text{g}) + \text{O}_2(\text{g}) \rightarrow 2\text{NO}_2(\text{g})\].

This intermediate, NO2, is integral to nitric acid production as it is the species that is absorbed by water to form nitric acid. Nitrogen oxides are also environmentally relevant as they are involved in the formation of acid rain and photochemical smog, which adds a dimension of environmental responsibility to the understanding of their chemistry. Mastery of nitrogen oxides chemistry is important for operating safely and sustainably in chemical industries.

Nitric acid synthesis during the Ostwald process features an elegant sequence of chemical reactions, starting with the catalytic oxidation of ammonia and ending with the absorption of nitrogen dioxide in water to produce nitric acid. The final chemical reactions involve the conversion of nitrogen dioxide into nitric acid, as follows:
\[3\text{NO}_2(\text{g}) + \text{H}_2\text{O}(l) \rightarrow 2\text{HNO}_3(\text{aq}) + \text{NO}(\text{g})\].

This reaction not only produces the desired nitric acid but also regenerates the nitric oxide, which is crucial for the economy of the process, as it is re-oxidized to continue the cycle. These reactions are carefully controlled in industrial settings to maximize production, minimize the release of nitrogen oxides into the atmosphere, and ensure optimal use of energy and resources. Understanding these reactions provides students with insights into practical applications of chemical principles and the importance of reaction control in industrial processes.