Question

Hydrogen for use in ammonia production is produced by the reaction $$\mathrm{CH}_{4}(g)+\mathrm{H}_{2} \mathrm{O}(g) \frac{\text { Nicatalyst }}{750^{\circ} \mathrm{C}} \mathrm{CO}(g)+3 \mathrm{H}_{2}(g)$$ What will happen to a reaction mixture at equilibrium if a. \(\mathrm{H}_{2} \mathrm{O}(g)\) is removed? b. the temperature is increased (the reaction is endothermic)? c. an inert gas is added to a rigid reaction container? d. \(\mathrm{CO}(g)\) is removed? e. the volume of the container is tripled?

Short answer

In summary: a. If H2O(g) is removed, the reaction shifts to the left (toward the reactants). b. If the temperature is increased in an endothermic reaction, the reaction shifts to the right (toward the products). c. Adding an inert gas to a rigid reaction container does not change the equilibrium position. d. If CO(g) is removed, the reaction shifts to the right (toward the products). e. If the volume of the container is tripled, the reaction shifts to the right (toward the products) to re-establish equilibrium.

Step-by-step solution

Identify the side where H2O(g) is present.

In the given reaction, H2O(g) is on the reactant side.

Analyze the effect of removing H2O(g) on the equilibrium position.

According to Le Chatelier's principle, when H2O(g) is removed, the reaction will shift in the direction which will increase the concentration of H2O(g). Thus, the reaction will shift to the left (toward the reactants). #b. The temperature is increased (the reaction is endothermic)#

Analyze the effect of increasing temperature on the equilibrium position.

As the reaction is endothermic, it means the reaction absorbs heat to proceed. According to Le Chatelier's principle, upon increasing the temperature, the reaction will shift in the direction which absorbs the added heat. Hence, the reaction will shift to the right (toward the products). #c. An inert gas is added to a rigid reaction container#

Analyze the effect of adding an inert gas on the equilibrium position.

In a rigid reaction container, when an inert gas is added, the overall pressure increases but the partial pressures of each component remain unchanged. Since the equilibrium position doesn't rely on the total pressure but only on the partial pressures, the addition of an inert gas in a rigid reaction container does not cause a shift in the equilibrium position. #d. CO(g) is removed#

Identify the side where CO(g) is present.

In the given reaction, CO(g) is on the product side.

Analyze the effect of removing CO(g) on the equilibrium position.

According to Le Chatelier's principle, when CO(g) is removed, the reaction will shift in the direction which will increase the concentration of CO(g). Thus, the reaction will shift to the right (toward the products). #e. The volume of the container is tripled#

Analyze the effect of tripling the volume on the equilibrium position.

When the volume of the container is tripled, the pressure in the system decreases. According to Le Chatelier's principle, the reaction will shift in the direction which has more moles of gas to counteract the change in pressure. Since there are 2 moles of gas on the reactant side and 4 moles of gas on the product side, the reaction will shift to the right (toward the products) to re-establish equilibrium.

Key concepts

Le Chatelier's Principle

Le Chatelier's Principle is a fundamental concept in chemical equilibrium that helps predict how a system at equilibrium will react to changes in conditions. It states that if a dynamic equilibrium is disturbed by altering the conditions, the system adjusts itself to counteract the effect of the disturbance and establish a new equilibrium. This principle can be applied to situations where there are changes in concentration, pressure, or temperature.

For example:

• If a reactant is removed from a system at equilibrium, the equilibrium will shift to produce more of the removed substance.
• Adding a reactant will cause the system to shift toward the products.
• If a product is removed, the equilibrium shifts to produce more product.

This behavior is essentially the system's way of "compensating" for the change, striving to restore balance. Understanding this principle helps predict the direction of shifts and the resulting changes in concentrations of reactants and products.

Endothermic Reaction

An endothermic reaction is a chemical reaction that absorbs heat from its surroundings. In thermodynamic terms, it requires an input of energy, making the surroundings cooler. This can often be observed when there is an increase in temperature which in itself is a key factor influencing the direction of the reaction.

In the context of Le Chatelier's Principle, increasing the temperature in an endothermic reaction will cause the equilibrium to shift toward the products. This is because the system seeks to absorb the added heat, aligning with the reaction's heat absorption property.

This kind of reaction context is common in industrial settings, such as the formation of hydrogen gas from methane and steam, which is used in synthesizing ammonia. These processes rely on adjusting temperatures to manage and optimize reaction outputs, affecting the equilibrium accordingly.

Reaction Kinetics

Reaction kinetics explores the speed or rate of chemical reactions and how different conditions like concentration, temperature, and catalysts affect this rate. It provides insight into how quickly a reaction will reach equilibrium, but not the position of the equilibrium itself.

Catalysts, for example, are substances that increase the rate of a reaction without being consumed, by lowering the activation energy needed for the reaction. This means that in an industrial context, catalysts can be employed to speed up the reaction, allowing for quicker attainment of equilibrium.

However, it is crucial to note that while reaction kinetics can change the rate of reaching equilibrium, they do not shift the equilibrium position. The position is strictly determined by the thermodynamics of the reaction - as depicted in equilibrium constants - not by how fast the reaction occurs.

Gas Laws

Gas laws describe the behavior of gases and how they interact under various conditions of pressure, volume, and temperature. These laws are crucial when considering reactions involving gaseous components.

For chemical equilibrium in gaseous systems, changes in pressure and volume can lead to shifts as predicted by Le Chatelier's Principle. For instance:

• When the volume of a system is increased, the pressure decreases, prompting the equilibrium to shift toward the side with more moles of gas.
• If volume decreases, the pressure increases, causing the system to favor the side with fewer moles of gas.

Understanding gas laws is essential in managing reactions in industrial processes, allowing for precise control over reaction conditions to promote efficiency and efficacy. These concepts are particularly pertinent in processes like gas formation and extraction, where optimizing equilibrium is necessary for maximizing yields.