Question

This reaction is exothermic. $$ \mathrm{C}_{2} \mathrm{H}_{4}(g)+\mathrm{Cl}_{2}(g) \rightleftharpoons \mathrm{C}_{2} \mathrm{H}_{4} \mathrm{Cl}_{2}(g) $$ If you were a chemist trying to maximize the amount of \(\mathrm{C}_{2} \mathrm{H}_{4} \mathrm{Cl}_{2}\) produced, which of the following might you try? Assume that the reaction mixture reaches equilibrium. (a) increasing the reaction volume (b) removing \(\mathrm{C}_{2} \mathrm{H}_{4} \mathrm{Cl}_{2}\) from the reaction mixture as it forms (c) lowering the reaction temperature (d) adding \(\mathrm{Cl}_{2}\)

Short answer

To maximize the production of C2H4Cl2, strategies (b) removing C2H4Cl2 as it forms, (c) lowering the reaction temperature, and (d) adding more Cl2 would be effective.

Step-by-step solution

Understand the System in Terms of Le Chatelier's Principle

Le Chatelier's Principle states that if an external change is imposed on a system at equilibrium, the system adjusts in such a way as to counteract the imposed change and a new equilibrium is established. For reactions, these changes could be in concentration, volume, temperature, or pressure.

Evaluate Option (a) Increasing the Reaction Volume

Increasing the volume of the reaction will shift the equilibrium toward the side with more moles of gas. In this case, the reaction already has an equal amount of moles of gas on both sides (1 mole of C2H4 and 1 mole of Cl2 versus 1 mole of C2H4Cl2), so changing the volume would not affect the equilibrium significantly towards producing more product.

Assess Option (b) Removing C2H4Cl2 as it Forms

Removing one of the products from the reaction mixture, in this case, C2H4Cl2, will shift the equilibrium towards the products side to fill the 'gap', according to Le Chatelier's Principle. This will result in the formation of more C2H4Cl2.

Consider Option (c) Lowering the Reaction Temperature

Since the reaction is exothermic, lowering the temperature has the effect of shifting the equilibrium towards the production of more heat, which in this case is the product side. Therefore, lowering the temperature would result in the formation of more C2H4Cl2.

Evaluate Option (d) Adding Cl2

Adding more of a reactant, such as Cl2, would shift the equilibrium towards the right to produce more products as the system seeks to re-establish equilibrium. Thus, this would increase the amount of C2H4Cl2 produced.

Determining the Best Method

Based on Le Chatelier's Principle, to maximize the production of C2H4Cl2, the most effective methods would be removing C2H4Cl2 as it forms (b), lowering the reaction temperature (c), and adding more Cl2 (d).

Key concepts

Equilibrium Chemistry

Equilibrium chemistry is a fundamental concept in the study of chemical reactions. It describes the state where the rate of the forward reaction equals the rate of the reverse reaction, resulting in no net change in the concentrations of reactants and products. This balance is what we refer to as a dynamic equilibrium. Importantly, it's dynamic because the reactions are still proceeding, but in such a way that their effects cancel out.

When a system is at equilibrium and experiences a disturbance, Le Chatelier's Principle comes into play. This principle helps predict how the system adjusts to restore a new equilibrium. Changes that can affect equilibrium include alterations in concentration, pressure, volume, and temperature. For instance, if you remove a product from the equilibrium mixture, as is suggested with option (b) in the exercise, the reaction will adjust to produce more of the removed product, thus shifting the equilibrium toward the product side.

Exothermic Reactions

Exothermic reactions are chemical processes that release energy, typically in the form of heat, into their surroundings. This means that the total energy of the product molecules is lower than that of the reactant molecules. Therefore, for exothermic reactions, heat can be considered a product of the reaction.

Understanding whether a reaction is exothermic is crucial when applying Le Chatelier's Principle. In the context of the given exercise, lowering the temperature, as suggested in option (c), would favor the production of more C2H4Cl2. This is because according to Le Chatelier's Principle, reducing the temperature of an exothermic reaction causes the system to produce more heat as part of re-establishing equilibrium, which correlates with the formation of more products.

Chemical Equilibrium Adjustment

Chemical equilibrium adjustment refers to the changes that occur in a system in response to an external stress applied to it while it is in a state of equilibrium. Le Chatelier's Principle provides insight into the behaviour of the system in attempting to counteract these changes.

In practical applications like manufacturing, knowing how to adjust the conditions to shift the equilibrium in favor of desired products is invaluable. For the reaction outlined in the exercise, options (b), removing C2H4Cl2, and (d), adding Cl2, would shift the equilibrium towards the right, enhancing product formation. This illustrates chemical equilibrium adjustment through changes in concentration. However, option (a) isn't useful because the reaction involves equal moles of gaseous reactants and products; thus, a change in volume doesn't have a significant impact on shifting the equilibrium in either direction.