CHM 301 — Physical Chemistry II: Lecture Note

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This is the complete lecture note for CHM 301 Physical Chemistry II. You can read it online below, open it in the full viewer, or download the PDF for offline study. It pairs with the course's video lectures, so you can read and watch together.

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LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS

LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS Course code: CHM 301 Course title: Physical Chemistry II Course unit: 2 Units Series 1: Foundations of Gibbs Function in Physical Chemistry Part 1 Concept and Definition of Gibbs Function • 1.1.1 Historical background of Gibbs Function • 1.1.2 Definition and mathematical formulation • 1.1.3 Physical significance in chemical systems Part 2 Properties and Applications of Gibbs Function • 1.2.1 Relationship with spontaneity of reactions • 1.2.2 Gibbs Function and equilibrium conditions • 1.2.3 Practical examples in chemical thermodynamics Part 3 Extensions of Gibbs Function in Physical Chemistry • 1.3.1 Gibbs Function in phase transitions • 1.3.2 Gibbs Function in electrochemical systems • 1.3.3 Limitations and scope of Gibbs Function Introduction In chemical sciences, predicting whether a reaction will occur spontaneously is one of the most important questions a chemist can ask. The Gibbs Function, also known as Gibbs free energy, provides a powerful tool for answering this question. It connects energy changes in chemical systems with equilibrium and spontaneity, making it central to the study of physical chemistry. By exploring its foundations, you will gain insight into how chemical processes are driven and controlled, which is essential for understanding the broader themes of thermodynamics and kinetics in this course. The aim of this Series is to introduce you to the fundamental aspects of Gibbs Function, to explain its properties and applications, and to demonstrate how it extends into different areas of physical chemistry. By the end of this Series, you will be able to define, analyse, and apply Gibbs Function to chemical systems with confidence. We shall commence this Series by examining the concept and definition of Gibbs Function, including its historical background, mathematical formulation, and physical significance. Next,

LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS we will move on to its properties and applications, focusing on how Gibbs Function relates to spontaneity, equilibrium, and practical examples in thermodynamics. Finally, we will conclude by considering extensions of Gibbs Function in physical chemistry, such as its role in phase transitions and electrochemical systems, while also reflecting on its limitations and scope. This sequential approach will provide you with a solid foundation for applying Gibbs Function in both theoretical and practical contexts. Series Learning Outcomes Upon completing this Series, you should be able to: • define the Gibbs Function and outline its historical background, • explain the mathematical formulation of Gibbs Function and interpret its physical significance in chemical systems, • analyse how Gibbs Function determines the spontaneity of chemical reactions, • demonstrate the use of Gibbs Function in establishing equilibrium conditions, • apply Gibbs Function to practical examples in chemical thermodynamics, • evaluate the role of Gibbs Function in phase transitions, • illustrate the application of Gibbs Function in electrochemical systems, and • assess the limitations and scope of Gibbs Function within physical chemistry. 1.1 Concept And Definition Of Gibbs Function 1.1.1 Historical background of Gibbs Function The Gibbs Function, also called Gibbs free energy, was introduced by Josiah Willard Gibbs in the late nineteenth century. Gibbs was a pioneer in chemical thermodynamics, and his work provided a systematic way to predict whether chemical or physical processes would occur spontaneously under given conditions. Before his contribution, chemists relied heavily on experimental trial and error to determine reaction feasibility. Gibbs’ formulation offered a theoretical framework that connected energy, entropy, and equilibrium. This historical perspective helps us appreciate why Gibbs Function is central to physical chemistry. It is not merely a mathematical expression but a tool that transformed the way chemists understand and predict chemical behaviour.

LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS Fill in the blank: The scientist who introduced the Gibbs Function was __________. Figure 1.1 Historical background of Gibbs Function 1.1.2 Definition and mathematical formulation Gibbs Free Energy The Gibbs Function (or Gibbs Free Energy) is a thermodynamic potential that represents the maximum reversible work obtainable from a system at constant temperature and pressure. It is mathematically expressed as: G = H − T · S Where: • H (enthalpy): the total heat content of the system • T (temperature): the absolute temperature measured in Kelvin • S (entropy): the degree of disorder or randomness in the system This formulation shows that Gibbs Free Energy combines both energy and disorder to determine the feasibility of a process. The change in Gibbs Free Energy, denoted as ΔG, is especially important: • ΔG < 0: the process is spontaneous

LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS • ΔG = 0: the system is at equilibrium • ΔG > 0: the process is non-spontaneous Thus, Gibbs Free Energy provides a direct criterion for predicting chemical behaviour under constant temperature and pressure. Fill in the blank: A process is at equilibrium when the change in Gibbs Function ((\Delta G)) is __________. Figure 1.2 Mathematical formulation of Gibbs Function 1.1.3 Physical Significance in Chemical Systems The physical significance of the Gibbs Function lies in its ability to predict the direction and feasibility of chemical processes. When a system undergoes a change at constant temperature and pressure, the Gibbs Function indicates whether the process will be spontaneous, at equilibrium, or non-spontaneous. • ΔG < 0 → The process is spontaneous, meaning it can occur without external intervention. • ΔG = 0 → The system is at equilibrium, and no net change occurs. • ΔG > 0 → The process is non-spontaneous, requiring external energy input to proceed.

LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS This makes Gibbs Function a central tool in chemical thermodynamics, as it connects energy changes with observable chemical behaviour. For example, in biochemical systems, Gibbs Function helps explain how reactions in living organisms proceed efficiently under mild conditions. Fill in the blank: A process is spontaneous when the change in Gibbs Function ((\Delta G)) is __________. Figure 1.3 Physical significance of Gibbs Function in chemical systems Pilot questions 1.1 1. Who introduced the concept of Gibbs Function in the nineteenth century? 2. Write the mathematical expression for Gibbs Function. 3. Identify the thermodynamic quantities represented by H, T, and S in the Gibbs Function equation. 4. State the condition of Gibbs Function for a process to be spontaneous. 5. What does it mean when ΔG = 0? 1.2 Properties And Applications Of Gibbs Function 1.2.1 Relationship with spontaneity of reactions The spontaneity of a chemical reaction refers to whether it can occur naturally without external intervention. The Gibbs Free Energy provides a direct criterion for spontaneity:

LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS • ΔG < 0 → The reaction is spontaneous. • ΔG = 0 → The system is at equilibrium. • ΔG > 0 → The reaction is non-spontaneous. This property is extremely useful because it allows chemists to predict reaction behaviour before conducting experiments. For example, in industrial chemistry, knowing whether a reaction is spontaneous helps in designing efficient processes. Fill in the blank: A chemical reaction is spontaneous when the change in Gibbs Function ΔG is __________. Figure 1.4 Relationship between Gibbs Function and spontaneity of reactions 1.2.2 Gibbs Function and equilibrium conditions The equilibrium condition in a chemical system is reached when the forward and reverse reactions occur at equal rates, resulting in no net change in the system. Gibbs Function provides a mathematical way to identify this state. At equilibrium, ΔG = 0. This means that the system has reached a balance where energy is optimally distributed, and no further work can be extracted. Understanding this property is crucial in chemical thermodynamics, as it explains why certain reactions stop progressing even though reactants are still present.

LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS Fill in the blank: At equilibrium, the change in Gibbs Function ΔG is __________. Figure 1.5 Gibbs Function and equilibrium conditions 1.2.3 Practical examples in chemical thermodynamics The Gibbs Function is applied in many practical contexts within chemical thermodynamics. For instance: • In predicting whether a reaction will occur under given temperature and pressure conditions. • In determining the feasibility of biochemical reactions, such as those in cellular metabolism. • In industrial processes, such as the production of ammonia in the Haber process, where Gibbs Function helps optimise reaction conditions. By applying Gibbs Function, chemists can design processes that are both efficient and cost-effective. It also provides insight into why certain reactions require catalysts or specific environmental conditions to proceed. Fill in the blank: The Gibbs Function is widely applied in industrial chemistry, for example in the __________ process. Pilot questions 1.2 1. What condition of Gibbs Function indicates that a reaction is spontaneous?

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