Question

Complete the following statements relating to the production of ammonia by the Haber process, for which the overall reaction is \(\mathrm{N}_{2}(\mathrm{~g})+3 \mathrm{H}_{2}(\mathrm{~g}) \longrightarrow 2 \mathrm{NH}_{3}(\mathrm{~g}) \cdot\) (a) The rate of consumption of \(\mathrm{N}_{2}\) is ______ times the rate of consumption of \(\mathrm{H}_{2}\). (b) The rate of formation of \(\mathrm{NH}_{3}\) is _____ times the _______times the rate of consumption of \(\mathrm{N}_{2}\).

Short answer

The rate of consumption of \(\mathrm{N}_{2}\) is \(1/3\) times the rate of consumption of \(\mathrm{H}_{2}\). The rate of formation of \(\mathrm{NH}_{3}\) is 2 times the rate of consumption of \(\mathrm{N}_{2}\).

Step-by-step solution

Analyze the balanced chemical equation

The balanced chemical equation for the production of ammonia is: \(\mathrm{N}_{2}(\mathrm{g}) + 3 \mathrm{H}_{2}(\mathrm{g}) \longrightarrow 2 \mathrm{NH}_{3}(\mathrm{g})\). This indicates that 1 mole of nitrogen gas \(\mathrm{N}_{2}\) reacts with 3 moles of hydrogen gas \(\mathrm{H}_{2}\) to produce 2 moles of ammonia \(\mathrm{NH}_{3}\).

Determine the ratio of consumption of \(\mathrm{N}_{2}\) to \(\mathrm{H}_{2}\)

From the chemical equation, it can be seen that for every mole of \(\mathrm{N}_{2}\) consumed, 3 moles of \(\mathrm{H}_{2}\) are consumed. Therefore, the rate of consumption of \(\mathrm{N}_{2}\) is \(1/3\) times the rate of consumption of \(\mathrm{H}_{2}\).

Determine the rate of formation of \(\mathrm{NH}_{3}\) compared to the rate of consumption of \(\mathrm{N}_{2}\)

According to the chemical equation, two moles of \(\mathrm{NH}_{3}\) are produced for every mole of \(\mathrm{N}_{2}\) consumed. Therefore, the rate of formation of \(\mathrm{NH}_{3}\) is 2 times the rate of consumption of \(\mathrm{N}_{2}\).

Key concepts

Chemical Reaction Stoichiometry

Understanding chemical reaction stoichiometry is crucial for scientists and engineers who design reactions for chemical synthesis, including the Haber process for producing ammonia. Stoichiometry is the calculation of reactants and products in chemical reactions. In stoichiometry, the balance of atoms and the conservation of mass principle are applied to arrive at a balanced equation, indicating the proportions of reactants needed to yield a specified amount of product.

For instance, looking at the balanced equation for the Haber process \( \mathrm{N}_{2}(\mathrm{~g}) + 3 \mathrm{H}_{2}(\mathrm{~g}) \longrightarrow 2 \mathrm{NH}_{3}(\mathrm{~g}) \), one can decipher the mole ratio between reactants and products. This ratio tells us that one mole of nitrogen gas \( \mathrm{N}_{2} \) reacts with three moles of hydrogen gas \( \mathrm{H}_{2} \) to produce two moles of ammonia \( \mathrm{NH}_{3} \). This is essential in predicting how much reactants are needed and how much product will form in a real-world chemical process like the Haber process.

Rates of Reaction

When it comes to the production of industrial chemicals, the rate of reaction is just as important as the stoichiometry. The rate at which reactants turn into products can significantly influence the efficiency and cost-effectiveness of a process. The reaction rate can be understood as the speed at which a chemical reaction proceeds, typically measured in terms of how fast a reactant is consumed or a product is formed over time.

In the Haber process for ammonia synthesis, the rate at which nitrogen \( \mathrm{N}_{2} \) and hydrogen \( \mathrm{H}_{2} \) gases are consumed, and ammonia \( \mathrm{NH}_{3} \) is created, is guided by their stoichiometric ratios. For every mole of nitrogen consumed, three moles of hydrogen are consumed, and two moles of ammonia are produced. Consequently, if we were to measure the rates, we'd find that nitrogen gas is consumed at a rate that is one-third the rate of hydrogen gas consumption, and ammonia is formed at twice the rate at which nitrogen is consumed. These rates are intrinsic to the efficiency of the reaction and ultimately determine the production rate of ammonia in the industry.

Ammonia Synthesis

Ammonia synthesis via the Haber process is a significant industrial chemical reaction that provides the world with one of its most important chemicals, ammonia. The process combines nitrogen from the air with hydrogen derived mainly from natural gas (methane) into ammonia. The ammonia produced is a key ingredient in the manufacture of fertilizers, which are essential in modern agriculture.

The synthesis of ammonia is not straightforward, given that it involves reaction temperatures of approximately 450-500°C and pressures of 150-200 atmospheres. In addition, a catalyst composed of iron mixed with small amounts of other substances is used to increase the rate of reaction without being consumed in the process. The intricacies of ammonia synthesis are a testament to the importance of understanding stoichiometry, reaction rates, and chemical kinetics in order to optimize a pivotal process that enables the large-scale production of fertilizer. These factors work together to ensure the Haber process is as efficient, cost-effective, and environmentally friendly as possible.