Question

The synthesis of \(\mathrm{NH}_{3}\) uses this chemical reaction. \(\mathrm{N}_{2}(\mathrm{~g})+3 \mathrm{H}_{2}(\mathrm{~g}) \rightleftarrows 2 \mathrm{NH}_{3}(\mathrm{~g})+92 \mathrm{~kJ}\) Identify three stresses that can be imposed on the equilibrium to maximize the amount of \(\mathrm{NH}_{3}\).

Short answer

Lower temperature, increase pressure, and increase reactant concentration.

Step-by-step solution

Understanding Equilibrium

The given reaction is \[ \mathrm{N}_{2}(\mathrm{~g}) + 3 \mathrm{H}_{2}(\mathrm{~g}) \rightleftarrows 2 \mathrm{NH}_{3}(\mathrm{~g}) + 92 \mathrm{~kJ} \]This is an exothermic reaction since heat is produced. According to Le Chatelier's Principle, the system wants to oppose changes that affect the equilibrium. So, any stress imposed on the system will result in a shift that minimizes that effect.

Stress 1: Change in Temperature

Since this is an exothermic reaction (releases heat), lowering the temperature will shift the equilibrium towards producing more \( \mathrm{NH}_3 \). The system will compensate by favoring the exothermic direction to release heat and counterbalance the temperature drop.

Stress 2: Change in Pressure

In the given reaction, 4 moles of gas (\( \mathrm{N}_2 + 3 \mathrm{H}_2\)) on the reactant side produce 2 moles of \( \mathrm{NH}_3 \) on the product side. Increasing pressure will shift the equilibrium toward the side with fewer moles of gas, in this case, the product side, forming more \( \mathrm{NH}_3 \).

Stress 3: Change in Concentration

Increasing the concentration of either \( \mathrm{N}_2 \) or \( \mathrm{H}_2 \) will shift the equilibrium toward the right, producing more \( \mathrm{NH}_3 \). By saturating the reaction with reactants, the system favors forming more products to restore balance.

Key concepts

Le Chatelier's Principle

Le Chatelier's Principle is a fundamental concept in chemical equilibrium. It explains how a system at equilibrium reacts to changes, or "stresses," to restore balance. Think of it as the reaction's way of staying comfortable under new conditions. If a change occurs, the system will shift its equilibrium position to counteract the stress.
For example, if you add more of a reactant in a chemical reaction, the system will try to balance it out by creating more products. Conversely, if you remove a product, the system will shift towards the product side to replace what's lost.
The principle is easy to apply when you remember that a chemical system resists changes to its equilibrium like a spring returning to its original shape. This concept is particularly useful in industrial chemical processes to maximize yield.

Exothermic Reactions

In an exothermic reaction, heat is released as a byproduct. This is like how a campfire gives off warmth as it burns. It's important to understand these reactions because they play a crucial role in chemical processes, including many chemical syntheses.
With exothermic reactions, a decrease in temperature will shift the balance towards the products. It's like the reaction is trying to stay warm, so it generates more heat by converting reactants into products. This shift is crucial in optimizing reactions for increased yields, such as in the production of ammonia ( NH_3 ).
Using exothermic reactions wisely involves manipulating temperature to drive equilibrium in a direction favorable for greater product formation. This understanding is crucial in industrial settings where maximizing output is key.

Chemical Synthesis

Chemical synthesis involves creating desired chemical products through controlled chemical reactions. It’s like following a recipe to bake a cake, but much more precise and often at a molecular level. In industry, this process is essential for producing pharmaceuticals, fertilizers, and countless other products.
For example, the synthesis of ammonia ( NH_3 ) is vital for agricultural fertilizers. Companies use processes such as the Haber process, which relies heavily on principles of chemical equilibrium and reaction conditions. By adjusting temperature, pressure, and concentrations of reactants, manufacturers optimize the yield of ammonia.
Understanding chemical synthesis involves more than just knowing the reaction; it requires an understanding of various conditions that affect reaction rates and product formation. This deeper knowledge allows chemists to design effective production methods that efficiently create the necessary compounds.