Lecture Notes: The Effect of Change in Concentration on Reversible Reactions at Equilibrium

Introduction

• Objective: Understand how changes in concentration affect reversible reactions at equilibrium.
• Audience: Higher-tier students.
• Previous Lesson Recap: Discussed reversible reactions and equilibrium.

Key Concepts

Equilibrium

• A reversible reaction in a sealed container reaches a point where forward and reverse reactions occur at the same rate.
• This point is called equilibrium.

Le Chatelier's Principle

• If a system is at equilibrium and a change is made to the conditions, the system will respond to counteract the change.
• It's important to understand how the system (or reaction) shifts to maintain equilibrium.

Effects of Concentration Changes

Example Reaction

• Reaction: [ NO_2 \leftrightarrow N_2O_4 ]
  • This is a reversible reaction.

Increasing NO2 Concentration

• Initial Change: Adding more ( NO_2 ) to the system.
• Effect: Equilibrium is disturbed because the forward and reverse reactions are no longer at the same rate.
• Response: More ( N_2O_4 ) will form until equilibrium is re-established.

Decreasing N2O4 Concentration

• Initial Change: Reducing the amount of ( N_2O_4 ) present.
• Effect: The system is no longer at equilibrium.
• Response: More ( NO_2 ) will react to form ( N_2O_4 ) until equilibrium is reached again.

Increasing N2O4 Concentration

• Initial Change: Increasing the amount of ( N_2O_4 ).
• Effect: The equilibrium is disturbed.
• Response: More ( N_2O_4 ) will convert into ( NO_2 ) until equilibrium is re-established.

Practice Questions

• Explore more questions and practice problems on the effect of concentration on reversible reactions.
• Reference: "Revision World Workbook" for additional exercises.

Summary

• By changing the concentration of reactants or products, the equilibrium shifts to counteract the change, as described by Le Chatelier's Principle.
• Understanding these principles helps predict the behavior of reactions under different conditions.