Lecture 8 1-25-08 Entropy

Lecture 8 1-25-08 Entropy - Grade Records Posted on Course...

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Grade Records Posted on Course Web Page http://www.chem.ucsb.edu/coursepages/ Click on Chem 1B: General Chemistry ( Watts ) Click on Online Grades ( Create account first! ) Fill in the required information to open your account Create Student Account or Make Changes to Account Class: Email: PERM Number: Choose Password: (4 digits) Confirm Password: Submit the information then use “find grade” Results For: watts, richard att1 1-14 : 5 att 2 1-18 : 5 quiz1 1-18 : 5
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Entropy Definition T q S rev = Δ The symbol “ S” always refers to a change on a reversible pathway between two thermodynamic states of a system. Reversible pathways are those in which each step is very, very small, and their direction can be changed by a very, very small reversal to return a system to its prior state.
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Entropy – What is it good for? • It is a tool that can be used to determine the direction of spontaneous and non- spontaneous processes • Usually it must be used with other tools such as q, w, H and E to make predictions regarding spontaneity • It can be used to quantitatively characterize systems at equilibrium
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Entropy – Energy Dispersion or Concentration • In most cases S cannot be used alone to predict anything. • It is a measure of energy dispersion or concentration within a system • It must be coupled with energy dispersion or concentration in the surroundings to determine whether energy is dispersed or concentrated in the universe .
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Some goals for Entropy • Learn how to quantitatively calculate entropies for some types of processes: constant temperature, constant volume, constant pressure • Learn how to combine entropy with other quantities to predict direction of spontaneous changes • Learn how to apply entropy to systems at equilibrium, equilibrium constants
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Entropy • There is only one reversible pathway
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Lecture 8 1-25-08 Entropy - Grade Records Posted on Course...

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