Question

The exothermic formation of \(\mathrm{ClF}_{3}\) is represented by the equation: \(\mathrm{Cl}_{2}(\mathrm{~g})+3 \mathrm{~F}_{2}(\mathrm{~g}) \rightleftharpoons 2 \mathrm{ClF}_{3}(\mathrm{~g}) ; \Delta \mathrm{H}=-329 \mathrm{~kJ}\). Which of the following will increase the quantity of \(\mathrm{CIF}_{3}\) in an equilibrium mixture of \(\mathrm{Cl}_{2}, \mathrm{~F}_{2}\) and \(\mathrm{ClF}_{3}\) ? (a) Increasing the temperature (b) Removing \(\mathrm{Cl}_{2}\)

Short answer

Neither increasing temperature nor removing \(\mathrm{Cl}_{2}\) will increase \(\mathrm{ClF}_{3}\).

Step-by-step solution

Understand Exothermic Reaction

The reaction \(\mathrm{Cl}_{2}(\mathrm{~g})+3 \mathrm{~F}_{2}(\mathrm{~g}) \rightleftharpoons 2 \mathrm{ClF}_{3}(\mathrm{~g})\) is exothermic, with \(\Delta \mathrm{H} = -329 \mathrm{~kJ}\). An exothermic reaction releases heat, and therefore, increasing the temperature will shift the equilibrium to favor the endothermic direction (reactants).

Apply Le Chatelier's Principle to Temperature Increase

According to Le Chatelier’s Principle, increasing the temperature of an exothermic reaction will decrease the formation of products. Therefore, increasing the temperature will not increase the quantity of \(\mathrm{ClF}_{3}\).

Consider Effect of Removing a Reactant

If \(\mathrm{Cl}_{2}\) is removed from the equilibrium mixture, according to Le Chatelier's Principle, the equilibrium will shift towards the reactant side to produce more \(\mathrm{Cl}_{2}\), thus decreasing \(\mathrm{ClF}_{3}\) quantity.

Choose the Correct Option

After analyzing both options, neither increasing the temperature nor removing \(\mathrm{Cl}_{2}\) will increase the \(\mathrm{ClF}_{3}\) quantity. Hence, neither option (a) nor (b) will increase \(\mathrm{ClF}_{3}\) in the mixture when considering standard options given.

Key concepts

Exothermic Reaction

An exothermic reaction is a type of chemical reaction that releases energy by light or heat into its surroundings. In the given reaction of chlorine (\(\mathrm{Cl}_2\)) and fluorine (\(\mathrm{F}_2\)) to form chlorine trifluoride (\(\mathrm{ClF}_3\)), the reaction releases 329 kJ of energy. This indicates that the system is losing energy as it progresses, which is characteristic of exothermic reactions.
As the reaction moves forward, the products have less energy than the reactants because some of the reactants' potential energy has been converted into thermal energy.

• Heat is viewed as a "product" in this context.
• This relationship is crucial when deciding how changes in conditions affect the position of equilibrium.

Understanding that the reaction is exothermic helps you predict how certain changes, like shifts in temperature, can influence the balance of products and reactants.

Chemical Equilibrium

Chemical equilibrium refers to the state in which both reactants and products are present in concentrations that have no further tendency to change with time. It is a balance achieved when the rates of the forward and reverse reactions are equal.
In the equation representing the formation of \(\mathrm{ClF}_3\), the symbols \(\rightleftharpoons\) show us the reaction is reversible and can reach equilibrium.

• At equilibrium, the concentrations of chlorine gas (\(\mathrm{Cl}_2\)), fluorine gas (\(\mathrm{F}_2\)), and chlorine trifluoride (\(\mathrm{ClF}_3\)) remain constant.
• It's important to note that equilibrium does not mean the reactants and products are equal in concentration, but simply that their concentrations stop changing.

At equilibrium, even though the reactants and products are forming at the same rate, external factors can affect this balance, shifting the equilibrium position one way or the other.

Temperature Effects on Equilibrium

Temperature changes can have significant effects on the equilibrium of a chemical reaction, particularly exothermic ones like the \(\mathrm{ClF}_3\) formation.
According to Le Chatelier's Principle, if a dynamic equilibrium is disturbed by changing the conditions, the position of equilibrium moves to counteract the change.

• In exothermic reactions, increasing the temperature adds heat, "a product," prompting the system to form more reactants to absorb the extra heat.
• This shifts the equilibrium towards the endothermic direction (reactants), resulting in fewer products.

So, for the exothermic reaction to produce more \(\mathrm{ClF}_3\), the temperature should ideally be decreased, encouraging more product formation to release heat. Understanding these temperature effects helps in controlling and predicting the outcomes of chemical processes, which is crucial in both industrial and laboratory settings.