Problem 54 - 43 Years JEE ADVANCED (1978-2020) + JEE MAIN Chapterwise & Topicwise Solved Papers Chemistry

Question

The equilibrium : $$ \begin{gathered} \text { [1989-1 Mark] } \\ \mathrm{SO}_{2} \mathrm{Cl}_{2}(\mathrm{~g}) \rightleftharpoons \mathrm{SO}_{2}(\mathrm{~g})+\mathrm{Cl}_{2}(\mathrm{~g}) \end{gathered} $$ is attained at \(25^{\circ} \mathrm{C}\) in a closed container and an inert gas, helium is introduced. Which of the following statements are correct? (a) Concentration of \(\mathrm{SO}_{2}, \mathrm{Cl}_{2}\) and \(\mathrm{SO}_{2} \mathrm{Cl}_{2}\) do not change (b) More chlorine is formed (c) Concentration of \(\mathrm{SO}_{2}\) is reduced (d) More \(\mathrm{SO}_{2} \mathrm{Cl}_{2}\) is formed.

Step-by-Step Solution

Answer

(a) is correct; concentrations do not change.

Step 1: Analyze the Effect of Inert Gas on Equilibrium

Understand that adding an inert gas like helium at constant volume does not affect the concentrations of substances in a reaction equilibrium. The presence of helium increases total pressure, but partial pressures of the reactants and products remain unchanged.

Step 2: Examine Concentration Changes

Realize that since partial pressures remain unchanged, the concentrations of \(\mathrm{SO}_{2}, \mathrm{Cl}_{2}, \mathrm{and\ } \mathrm{SO}_2\mathrm{Cl}_2\) do not change due to the introduction of an inert gas.

Step 3: Evaluate the Correct Answer

Based on the analysis in Steps 1 and 2, determine that statement (a) is correct as the concentrations of all species do not change. Statements (b), (c), and (d) require changes in concentration or pressure of reactants/products, which do not occur here.

Key Concepts

Le Chatelier's Principle

Le Chatelier's principle helps us predict how a system in chemical equilibrium responds to external changes. When a system at equilibrium is disturbed, it will adjust to minimize the imposed change and re-establish equilibrium. This principle can be applied to shifts in concentration, temperature, pressure, or volume.

If you increase the concentration of a reactant, the system will shift to produce more products, and vice versa. Similarly, changes in pressure or temperature can drive the equilibrium in a direction that offsets the disturbance. This way, Le Chatelier's principle is like a guiding rule that chemistry uses to restore balance. It is crucial in understanding the dynamics of chemical reactions and predicting how equilibrium is affected by changes such as pressure or concentration.

Inert Gas Effect

Sometimes, chemists introduce inert gases into a reaction system. While it may seem like this could change things, inert gases (like helium) do not engage in chemical reactions with reactants or products. This property is why they are called "inert."

• When adding an inert gas at constant volume, it increases the total pressure of the system.
• However, it does not alter the partial pressures of reactants and products involved in the equilibrium.

Because the partial pressures remain the same, the equilibrium concentrations of the reactants and products do not change. Therefore, in situations like the introduction of helium into a reaction system, no shift in equilibrium occurs. This is an excellent example of a practical application of chemical equilibrium concepts, where you can observe the inert gas effect in action.

Equilibrium Concentration

Equilibrium concentration refers to the concentrations of reactants and products in a chemical reaction at equilibrium. For a reversible reaction, these concentrations remain constant over time when the system is closed and no changes are introduced.

Understanding equilibrium concentrations is vital in predicting and calculating how concentrations might change if the reaction conditions alter. In practice:

• If you change the concentration of reactants, the system adjusts to restore equilibrium, altering the equilibrium concentrations.
• However, unwanted or inert elements, like adding an inert gas without changing volume, typically don't affect the equilibrium concentrations.

In essence, equilibrium concentration is about the balance your system reaches naturally, and it's important for maintaining stability unless something actively shifts the balance like a change in temperature or pressure.

Reaction Dynamics

Reaction dynamics give us insights into how reactions proceed and how quickly they do so. It's the study of the rates and pathways of chemical reactions, providing a detailed description of the transformations occurring at the molecular level.

• Understanding these dynamics is key for controlling processes to synthesize desired products more efficiently.
• Even tiny changes in conditions like pressure, temperature or concentration can dramatically alter the speed and outcome of a reaction.

Within equilibrium contexts, dynamics tell us how quickly a system rebalances itself when disturbed. While the addition of an inert gas like helium may alter total system pressure, it doesn't change the speed at which equilibrium is reached if the conditions remain constant otherwise. Thus, reaction dynamics explore both the minute details of reaction pathways and broader trends in how conditions perpetuate or dampen these transformations over time.