Question

Hydrogen for use in ammonia production is produced by the reaction $$ \mathrm{CH}_{4}(g)+\mathrm{H}_{2} \mathrm{O}(g) \stackrel{\mathrm{Ni}_{2} \mathrm{catalyst}}{750^{\circ} \mathrm{C}} \mathrm{CO}(g)+3 \mathrm{H}_{2}(g) $$ 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

a. The reaction will shift to the left, producing more H₂O(g). b. The reaction will shift to the right, favoring the formation of CO(g) and H₂(g). c. No shift in the reaction will occur as there is no effect on concentrations. d. The reaction will shift to the right, producing more CO(g). e. The reaction will shift to the right, favoring the side with more moles of gas.

Step-by-step solution

Identify the direction of the shift

In this case, we're removing H₂O(g) from the reaction mixture. Le Châtelier's Principle states that the reaction will try to compensate for the change by shifting to the side to produce more H₂O(g). This means the reaction will shift to the left direction. #Part b: Increasing the temperature#

Identify the effect of the temperature on the reaction direction

The given reaction is endothermic, meaning it absorbs heat. According to Le Châtelier's Principle, when the temperature is increased, the reaction will shift in the direction in which heat is absorbed. In this case, the reaction will shift to the right, favoring the formation of CO(g) and H₂(g). #Part c: Adding an inert gas to a rigid reaction container#

Analyze the effect of adding an inert gas

When an inert gas is added to a rigid reaction container, it increases the overall pressure without directly affecting the concentrations of the reacting components. According to Le Châtelier's Principle, since there's no effect on concentrations, the position of the equilibrium does not change, and there will be no shift in the reaction. #Part d: Removing CO(g)#

Identify the direction of the shift

In this case, we're removing CO(g) from the reaction mixture. The system will try to compensate for the sudden decrease in concentration by shifting to the side where CO(g) is being produced. This means the reaction will shift to the right direction. #Part e: Tripling the volume of the container#

Analyze the effect of changing the volume

When the volume of a container is tripled, the concentrations of all substances will decrease. A larger volume means lower pressure. According to Le Châtelier's Principle, when the pressure is lowered, the reaction will try to compensate by shifting to the side with more moles of gas to increase the pressure.

Identify the direction of the shift

We need to identify the side with more moles of gas. On the reactants' side, there are 1 + 1 = 2 moles of gas, whereas on the products' side, there are 1 + 3 = 4 moles of gas. The reaction will shift to the side with more moles of gas; in this case, the reaction will shift to the right direction.

Key concepts

Chemical Equilibrium

Understanding the balance in chemical reactions is essential, and that's where chemical equilibrium comes into play. In a system at equilibrium, the rate of the forward reaction equals the rate of the reverse reaction, meaning substances are produced and consumed at the same pace. This results in constant concentrations of the reactants and products, even though they may not be equal.

To visualize this, imagine a perfectly balanced scale. When external conditions change (like pressure, concentration, or temperature), the scale tips one way or the other. That's what happens in a chemical system; it shifts to regain its balance, or equilibrium. Le Châtelier's Principle guides us in predicting how a chemical system at equilibrium reacts to these disturbances by shifting either to the right (toward products) or to the left (toward reactants). So, whether we're adding or removing a reactant or product, changing the volume of the container, or tweaking the temperature, understanding how equilibrium reacts helps us control chemical processes to our advantage.

Endothermic Reaction

Certain chemical reactions, like a hand warmer activated on a cold day, absorb energy from their surroundings. These are known as endothermic reactions. In these reactions, energy is essentially a 'reactant', and when the temperature increases, it's like adding more of this 'reactant' to the system.

Applying Le Châtelier's Principle, when we heat an endothermic reaction, it shifts to consume the extra heat, effectively shifting the equilibrium position to the right and resulting in more products. It's helpful to think of heat as an invisible participant in the reaction, which has its concentration changed by altering the temperature. By knowing if a reaction is endothermic (or its opposite, exothermic), we can influence the outcome – producing more of a desired product or conserving materials – by simply adjusting the temperature.

Reaction Shift

A reaction shift is the equilibrium's response to a change within the system, such as variations in concentration, pressure, or temperature. Le Châtelier's Principle helps predict the direction of this shift to restore balance. If there's a decrease in concentration of a product, the reaction will 'shift' to make more of that product. Conversely, if there's an increase, it will produce less. The same goes for reactants. It's a tug-of-war, and equilibrium is the rope.

When the volume of a system changes, it alters the pressure and thus the shift, with the reaction favoring the side with more or fewer gas moles depending on the specific volume change. Adding an inert gas at constant volume is a unique situation, it doesn't cause a shift since it doesn't change the concentration of reactants or products. These shifts are vital for industrial processes, where maximizing yield is key. Tweaking conditions to 'shift' reactions can dramatically affect the quantity and quality of the desired product.