Lecture 14: Gas-Liquid Equilibrium (Chapter 2)

LECTURE OVERVIEW:
In this lecture, we explore gas-liquid equilibrium in environmental systems, with a focus on understanding the differences between open and closed systems. We begin by distinguishing between these two types, emphasizing how gas exchange with the environment occurs in open systems, unlike closed systems where mass transfer is restricted. We then focus on the quantitative aspects of gas-liquid equilibrium, introducing key concepts such as Henry's law and how it governs the behavior of gases like CO2 in water. The lecture also covers the development of equilibrium expressions for gas-liquid systems, providing methods to calculate how gases like carbon dioxide dissolve and react in water. Finally, we construct pC-pH diagrams for a carbonate open system, demonstrating how the partial pressure of CO2 in the atmosphere impacts the speciation of carbonate, bicarbonate, and carbonic acid in aqueous systems.

INTENDED LEARNING OUTCOMES:
By the end of the lecture, you will be able to:
• Distinguish between open and closed environmental systems
• Quantify gas-liquid equilibrium expressions
• Construct the pC-pH diagram for a carbonate open system

RELEVANT READINGS:
• Water Chemistry, 2nd Edition, by Mark M. Benjamin
9. Gas/Liquid Equilibrium
9.1. Introduction
9.2. Basic Concepts and Terminology for Gas/Liquid Equilibrium
9.3. Effect of Gas/Liquid Equilibration on Gas-Phase Composition
9.4. Factors Affecting Volatility and Henry’s Constant
9.5. Henry’s Law and Aqueous-Phase Speciation
9.6. The pH of Solutions in Equilibrium with Acidic or Basic Gases
9.7. Gas-Liquid Equilibrium in Visual MINTEQ
• Environmental Chemistry, 10th Edition, by Stanley E. Manahan
2.6. Gases in Water
2.7. Carbon Dioxide in Water

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COURSE INFORMATION:
This video is part of the Environmental Chemistry course, designed and taught by Prof. Mim Rahimi. The course covers the following chapters: (1) Fundamentals of Environmental Chemistry, (2) Acids and Bases and Related Phenomena, (3) Chemistry of Metals, and (4) Redox Chemistry in Environmental Systems.

COURSE REFERENCES:
The recommended textbooks for the course are:
• Main Reference: Water Chemistry, 2nd Edition, by Mark M. Benjamin, Waveland Press Inc., ISBN: 978-1478623083
• Additional Useful Reference: Environmental Chemistry, 10th Edition, by Stanley E. Manahan, CRC Press, ISBN: 978-1032339726