Chapter 18: Chemical Thermodynamics
- Page ID
- 28593
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- Chapter 18.1: Thermodynamics and Work
- This page provides an overview of thermodynamics, focusing on systems, surroundings, state functions, and energy relationships. It defines a system and explores internal energy as a state function. Key aspects include the distinction between negative work (system to surroundings) and positive work (surroundings to system), with work varying by pathway.
- Chapter 18.2: The First Law of Thermodynamics
- This page covers the first law of thermodynamics, linking energy changes in systems to surroundings, highlighting that systems gravitate towards lower energy states. It defines internal energy change (ΔE = q + w) and introduces enthalpy (H) as significant in constant pressure contexts, equating ΔH to heat flow (qp). It further explores enthalpy in chemical reactions, notably combustion, addressing how structural variations in hydrocarbons affect enthalpy.
- Chapter 18.3: The Second Law of Thermodynamics
- This document from Howard University's General Chemistry course covers the principles of entropy and internal energy, focusing on the first and second laws of thermodynamics. It explains how entropy, a measure of system disorder, relates to spontaneous processes, using examples like heat flow, gas expansion, and phase transitions. Key concepts include calculating entropy changes, understanding reversible vs.
- Chapter 18.4: Entropy Changes and the Third Law of Thermodynamics
- This page covers thermodynamic cycles and their role in calculating changes in entropy (ΔS) using the "products minus reactants" method. It explains the third law of thermodynamics, highlighting that entropy is zero at absolute zero and positive above it. The page details calculating ΔS for reactions, especially combustion and phase transitions, using heat capacities and standard molar entropy (S°).
- Chapter 18.5: Free Energy
- This page details Gibbs free energy (ΔG) and its role in predicting the spontaneity of chemical reactions, particularly how ΔG varies with temperature, enthalpy (ΔH), and entropy (ΔS). It explains that ΔG < 0 indicates spontaneous processes, while ΔG > 0 signals non-spontaneity. The effects of temperature on reactions, including vaporization and metal carbonate decomposition, are emphasized, with examples provided.
- Chapter 18.6: Spontaneity and Equilibrium
- This page covers the relationship between Gibbs free energy (ΔG) and equilibrium constants (K), essential for determining reaction spontaneity. It explains how ΔG is influenced by enthalpy (ΔH°), entropy (ΔS°), and temperature, along with methods to calculate K at different temperatures. The page highlights the importance of reaction quotients (Q) in predicting product favorability by comparing it with ΔG°.
- Chapter 18.7: Comparing Thermodynamics and Kinetics
- This page elaborates on the distinctions between thermodynamics and kinetics in chemical reactions. Thermodynamics assesses reactions' equilibrium states and energetics, identifying spontaneous reactions, while kinetics focuses on the rates and pathways of these reactions. It highlights that non-spontaneous reactions can become spontaneous through coupling with favorable reactions, supported by practical examples such as metal extraction.
- Chapter 18.8: Thermodynamics and Life
- This page explores thermodynamics in biochemical systems, detailing how cells maintain a low-entropy state through energy exchanges, necessitating constant energy input. It describes energy acquisition methods via phototrophs and chemotrophs, emphasizing ATP and NADH's roles in metabolism. The function of NADH as an electron carrier during respiration is highlighted, alongside ATP's role in energy transfer and storage in fats, proteins, and sugars.
- Chapter 18.9: End of Chapter Material
- This page covers application problems in chemical reactions and thermodynamics, focusing on thermal energy storage, rocket fuel, heat loss, and fuel type comparisons. It involves calculations of enthalpy changes and spontaneity based on ΔH and ΔS. Additionally, it discusses heavy metal detoxification, explosive reactions, and thermodynamics of cadmium and ammonia.