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6. Equilibrium

Chemical equilibria are essential in biological and environmental processes, influencing reactions and substance interactions. The dynamic nature of equilibrium involves continuous particle exchange, leading to a constant vapor pressure in closed systems. Understanding the law of equilibrium, factors affecting it, and concepts like ionization are crucial for grasping the behavior of acids, bases, and salts in various reactions.

Sections

Equilibrium

Chemical equilibria play a vital role in biological and environmental processes, characterized by the balance of forward and reverse reactions.

6 Section Overview

Start current section content and materials

6.1 Equilibrium in Physical Process

This section explores the dynamic nature of equilibrium in physical processes, highlighting how vapour pressures, phase transformations, and various equilibrium systems operate.

6.1.1 Solid- liquid Equilibrium

This section discusses the concept of solid-liquid equilibrium, highlighting the dynamic processes that occur when ice and water coexist at melting point under specific conditions.

6.1.2 Liquid-Vapour Equilibrium

This section discusses the concept of liquid-vapour equilibrium, explaining how equilibrium is established in a closed system where molecules of a liquid evaporate into the gas phase and condense back into the liquid.

6.1.3 Solid – Vapour Equilibrium

This section discusses the equilibrium established between solid and vapor phases, focusing on the sublimation of solid iodine as a key example.

6.1.4 Equilibrium Involving Dissolution of Solid or Gases in Liquids

This section discusses the dynamic equilibrium established during the dissolution of solids and gases in liquids and the factors affecting it.

6.1.5 General Characteristics of Equilibria Involving Physical Processes

This section outlines the dynamic nature of equilibria in physical processes, emphasizing the characteristics and factors affecting equilibrium states.

6.2 EQUILIBRIUM IN CHEMICAL PROCESSES – DYNAMIC EQUILIBRIUM

The concept of dynamic chemical equilibrium describes the state where the concentrations of reactants and products remain constant over time due to equal rates of forward and reverse reactions.

6.3 Law of Chemical Equilibrium and Equilibrium Constant

This section explores the concept of chemical equilibrium, including the equilibrium constant and the law of mass action.

6.4 HOMOGENEOUS EQUILIBRIA

This section covers the fundamental principles of homogeneous equilibria, focusing on chemical and physical equilibrium processes within a single phase.

6.4.1 Equilibrium Constant in Gaseous Systems

This section discusses the concept of equilibrium constants in gaseous systems, focusing on the relationships between partial pressures and concentrations during chemical equilibria.

6.5 HETEROGENEOUS EQUILIBRIA

Heterogeneous equilibria occur in systems with multiple phases, such as solids, liquids, and gases, and can be analyzed using equilibrium constants while considering the effects of concentration changes and temperature.

6.6 Applications Of Equilibrium Constants

The section discusses the significance of equilibrium constants in predicting the extent and direction of chemical reactions.

6.6.1 Predicting the Extent of a Reaction

This section discusses how to predict the extent of a chemical reaction using equilibrium constants.

6.6.2 Predicting the Direction of the Reaction

This section discusses predicting the direction of chemical reactions using equilibrium constants and reaction quotients to determine whether a reaction is at equilibrium or which direction it will shift.

6.6.3 Calculating Equilibrium Concentrations

This section discusses the methods to calculate the equilibrium concentrations in a chemical reaction when the initial concentrations are known.

6.7 Relationship Between Equilibrium Constant K, Reaction Quotient Q And Gibbs Energy G

This section explores the relationship between the equilibrium constant (K), the reaction quotient (Q), and Gibbs energy (G), highlighting their significance in chemical equilibria.

6.8 Factors Affecting Equilibria

This section discusses the various factors that can influence the equilibrium state of chemical reactions.

6.8.1 Effect of Concentration Change

This section discusses the impact of changing the concentration of reactants or products on the dynamic equilibrium of a reaction.

6.8.2 Effect of Pressure Change

This section discusses how changes in pressure affect the position of equilibrium in gaseous reactions.

6.8.3 Effect of Inert Gas Addition

The addition of inert gases to a system at equilibrium does not disturb the equilibrium position, as it does not change the partial pressures or molar concentrations of the reactants and products.

6.8.4 Effect of Temperature Change

This section discusses how temperature changes affect the equilibrium state of chemical reactions, introducing concepts like exothermic and endothermic reactions, and the impact of temperature on equilibrium constants.

6.8.5 Effect of a Catalyst

A catalyst increases the rate of a chemical reaction without affecting the equilibrium composition.

6.9 IONIC EQUILIBRIUM IN SOLUTION

This section discusses ionic equilibrium in solutions, focusing on electrolytes and their classification as strong or weak based on ionization.

6.10 Acids, Bases and Salts

This section discusses the properties and roles of acids, bases, and salts in nature, along with their significance in everyday life.

6.10.1 Arrhenius Concept of Acids and Bases

The Arrhenius concept defines acids as substances that produce hydrogen ions in water, while bases produce hydroxide ions.

6.10.2 the brönsted- lowry Acids and bases

The Brönsted-Lowry theory defines acids as proton donors and bases as proton acceptors, expanding the understanding of acid-base chemistry.

6.10.3 Lewis Acids and Bases

This section introduces the concepts of Lewis acids and bases, defining acids as electron pair acceptors and bases as electron pair donors.

6.11 Ionization of Adids and Bases

This section discusses the ionization of acids and bases, highlighting the distinction between strong and weak electrolytes, and the concept of Ka and Kb.

6.11.1 The Ionization Constant of Water and its Ionic Product

This section discusses the ionization constant of water (Kw) and its importance in acid-base chemistry.

6.11.2 The pH Scale

The pH scale is a logarithmic scale used to quantify the acidity or alkalinity of a solution based on the concentration of hydrogen ions.

6.11.3 Ionization Constants of Weak Acids

This section discusses the ionization constants (Ka) of weak acids, their significance in determining acid strength, and their role in calculating concentrations of ions in solution at equilibrium.

6.11.4 Ionization of Weak Bases

The section explores the ionization of weak bases in aqueous solutions, including their equilibrium expressions and the factors affecting their ionization.

6.11.5 Relation Between Ka and Kb

The section discusses the relationship between the acid dissociation constant (Ka) and the base dissociation constant (Kb) for conjugate acid-base pairs.

6.11.6 Di- and Polybasic Acids and Di- and Polyacidic Bases

This section discusses the characteristics and ionization of di- and polybasic acids and their corresponding polyacidic bases.

6.11.7 Factors Affecting Acid Strength

The strength of an acid depends on several factors, including the bond strength and polarity of the H-A bond.

6.11.8 Common Ion Effect in the Ionization of Acids and Base

The common ion effect describes the reduction in solubility of an ionic compound when a strong electrolyte that shares a common ion is added to the solution, significantly impacting acid and base ionization.

6.11.9 Hydrolysis of Salts and the pH of their Solutions

This section discusses how salts formed from acids and bases undergo hydrolysis in water, affecting the pH of their solutions based on the strength of the acid and base from which they are derived.

6.12 Buffer Solutions

Buffer solutions are important in maintaining pH stability in biological and chemical systems.

6.12.1 Designing Buffewr Solution

This section discusses the principles of designing buffer solutions using weak acids and their salts or weak bases and their conjugate acids, highlighted by the Henderson–Hasselbalch equation.

6.13 SOLUBILITY EQUILIBRIA OF SPARINGLY SOLUBLE SALTS

This section discusses the solubility equilibria of sparingly soluble salts, emphasizing factors like lattice enthalpy and solvation enthalpy.

6.13.1 Solubility Product Constant

This section discusses the solubility product constant (Ksp) of sparingly soluble salts and its relevance in equilibrium chemistry.

6.13.2 Common Ion Effect on Solubility of Ionic Salts

The common ion effect describes how the solubility of an ionic salt decreases in a solution that contains a common ion, highlighting its impact on equilibrium.

6.14 Exercises

This section contains a variety of exercises designed to evaluate understanding of chemical equilibria.

6.15 SUMMARY

This section discusses the concept of chemical equilibrium, emphasizing its dynamic nature and how it relates to both physical and chemical processes.

Learning Objectives

  • Equilibrium is dynamic with equal rates of forward and reverse reactions.

  • Equilibrium constants (Kc, Kp) express the relationship between product and reactant concentrations.

  • Bufffer solutions resist pH changes and are vital in physiological and industrial contexts.

Key Concepts

Dynamic Equilibrium

A state of balance in which the rates of forward and reverse reactions are equal, leading to stable concentrations of reactants and products.

Equilibrium Constant (Kc)

A numerical value that represents the ratio of the concentration of products to reactants at equilibrium in a chemical reaction.

Le Chatelier’s Principle

This principle states that if a system at equilibrium is disturbed, the system will adjust itself to counteract the change and restore a new equilibrium.

Practice Exercises

Total Questions

2

Estimated Time

4 min

Passing Score

70%

Instructions

  • Read each question carefully
  • You can use hints if you need help
  • Complete all questions before submitting