LEC 23 CHAP 19

# LEC 23 CHAP 19 - Chapter 19 Why Study Entropy and Free...

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TOUPADAKIS Lecture 23 Chapter 19 Chapter 19 Why physical and chemical changes under specified conditions tend to be favored one direction over another? What is the connection between energy and the extent of a reaction? Does life violate the second law of thermodynamics? Why Study Entropy and Free Energy? In order to answer questions like: © 2004 A. Toupadakis

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TOUPADAKIS Lecture 23 Chapter 19 Chapter Learning Goals 1. Qualitatively determine whether simple chemical or physical changes are spontaneous. 2. Qualitatively predict whether the sign of Δ S is positive or negative for a chemical or physical change. 3. On the basis of probability, determine which of two states has the higher entropy. 4. Calculate the standard entropy of reaction from the standard molar entropies of products and reactants. 5. Determine whether a reaction is spontaneous by determining the sign of Δ S total. 6. Use the equation G = H - TS to calculate the free energy of reaction and to determine the temperature at which a nonspontaneous reaction becomes spontaneous. 7. Calculate the standard free energy of reaction from standard free energies of formation. 8. Calculate the free energy of reaction for a system having nonstandard pressures and concentrations. 9. From the standard free energy of reaction, calculate the value of the equilibrium constant.
TOUPADAKIS Lecture 23 Chapter 19 Lecture 23 Spontaneous Change: Definition and Examples. Non-spontaneous Change: Definition and Examples. When is a Change Spontaneous? The Concept of Entropy, S. Positional Entropy and Thermal Entropy. Statistical Definition of Entropy. Entropy Change of The System: Δ S system . Thermodynamic Definition of Entropy. Determination of Δ S total for a Physical Change: Spontaneous Physical State Change. Determination of Δ S total for a Physical Change: Physical State Change at Equilibrium. Second Law of Thermodynamics. Criterion for Spontaneous Change based on Δ S universe . Absolute Entropies and the Third Law of Thermodynamics. Standard Entropy of Reaction, Δ S o . Predicting Relative S o Values of a System. © 2004 A. Toupadakis

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TOUPADAKIS Lecture 23 Chapter 19 Spontaneity in Science We say that a system undergoes a spontaneous change (physical, or chemical) under specified conditions when the change occurs without a continuous input of energy in the form of work (directed energy) from the surroundings . In everyday use, “ spontaneous ” usually means impulsive or arising without forethought and often carries the implication of happening quickly. In science, spontaneous simply indicates that a change is possible or feasible and can occur; it implies nothing about speed. CHEMISTRY: A Project of the American Chemical Society, 2005.
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## This note was uploaded on 04/18/2010 for the course CHEM 2B 993029 taught by Professor Toupadakis during the Spring '10 term at UC Davis.

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LEC 23 CHAP 19 - Chapter 19 Why Study Entropy and Free...

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