Question

Docs Le Chatelier's principle predict a change of equilibrium concentration for the following reaction if the gas mixture is compressed. \(\mathrm{N}_{2} \mathrm{O}_{4}(\mathrm{~g}) \rightleftharpoons 2 \mathrm{NO}_{2}(\mathrm{~g})\) (1) Ycs, backward reaction is favoured. (2) Yes, forward reaction is favoured. (3) No changc. (4) No information.

Short answer

Option (1) Yes, backward reaction is favoured.

Step-by-step solution

Understand Le Chatelier's Principle

Le Chatelier's Principle states that if a dynamic equilibrium is disturbed by changing the conditions, the position of equilibrium moves to counteract the change.

Identify the Change

In this case, the change is the compression of the gas mixture which increases the pressure of the system.

Determine the Reaction's Response

The equilibrium will shift towards the side with fewer moles of gas to reduce the increased pressure. For this reaction, \(\text{N}_2\text{O}_4(\text{g}) \rightleftharpoons 2 \text{NO}_2(\text{g})\), the left side (N\text{N}_2\text{O}_4) has 1 mole of gas, whereas the right side (\text{2NO}_2) has 2 moles of gas.

Predict the Shift in Equilibrium

Since the left side (reactants) has fewer moles of gas, the equilibrium will shift to the left to reduce the increased pressure.

Select the Correct Option

Based on the analysis, the backward reaction is favored under compression. Thus, the correct option is: (1) Yes, backward reaction is favoured.

Key concepts

Chemical Equilibrium

Chemical equilibrium occurs in a reversible reaction when the rate of the forward reaction equals the rate of the backward reaction. At this point, the concentrations of reactants and products remain constant over time. This state can only be achieved in a closed system where no substances can enter or leave. The concept of chemical equilibrium is crucial for understanding how reactions behave under different conditions.
In our given problem, the reaction between dinitrogen tetroxide (\text{N}_2\text{O}_4) and nitrogen dioxide (\text{NO}_2) reaches an equilibrium point. The balanced equation is:
\[ \text{N}_2\text{O}_4(\text{g}) \rightleftharpoons 2\text{NO}_2(\text{g}) \]
At equilibrium, the amount of \text{N}_2\text{O}_4 and \text{NO}_2 is constant because the rate of conversion from \text{N}_2\text{O}_4 to \text{NO}_2 matches the rate of the reverse process.
This balance can be disturbed by changing conditions like pressure, temperature, or concentration. When such disruptions occur, the system will undergo adjustments to restore a new equilibrium state, as explained by Le Chatelier's Principle.

Pressure Effect on Gases

Pressure plays a significant role in reactions involving gases, particularly when system conditions change. According to Le Chatelier's Principle, if the pressure of a gas mixture at equilibrium is increased, the system will react by shifting the equilibrium towards the side with fewer gas molecules to decrease pressure. Conversely, decreasing pressure shifts the equilibrium towards the side with more gas molecules.
In the reaction \(\text{N}_2\text{O}_4(\text{g}) \rightleftharpoons 2 \text{NO}_2(\text{g})\), compressing the gas mixture increases the pressure. Looking at the molecular count:

• \text{N}_2\text{O}_4 has 1 mole of gas.
• \text{2NO}_2 has 2 moles of gas.

Given the increased pressure, the system will shift towards the left side of the reaction to reduce pressure, as there are fewer gas molecules (1 mole of \text{N}_2\text{O}_4 versus 2 moles of \text{NO}_2).
This is why the backward reaction is favored under compression.

Reaction Shift Direction

Understanding the direction in which a reaction will shift when equilibrium is disturbed is essential for predicting chemical behavior. Le Chatelier's Principle helps determine this direction: the system moves to counteract the change.
When pressure is increased in the reaction of \text{N}_2\text{O}_4 and 2\text{NO}_2, the equilibrium shifts left:
\[ \text{N}_2\text{O}_4(\text{g}) \rightleftharpoons 2\text{NO}_2(\text{g}) \]
Here’s why:

• Left side: 1 mole of \text{N}_2\text{O}_4.
• Right side: 2 moles of \text{NO}_2.

When the pressure increases, minimizing the number of gas molecules helps reduce this pressure. So, the equilibrium shifts toward \text{N}_2\text{O}_4, the side with fewer gas molecules, causing the backward reaction to be favored.
In conclusion, using Le Chatelier's Principle, we can predict shifts in equilibrium due to pressure changes. This understanding is both powerful and practical in fields like chemistry, engineering, and environmental science.