chem 1.1 chapter 19

chem 1.1 chapter 19 - Thermodynamics: Entropy and Free...

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General Chemistry II, Professor Maggie Ciszkowska General Chemistry II, Professor Maggie Ciszkowska Thermodynamics: Thermodynamics: Entropy and Free Energy Entropy and Free Energy Chapter 19 Chapter 19
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Thermodynamics is concerned with the question: Can a reaction occur ? First Law of Thermodynamics: energy is conserved . ( Chem 1 ) Any process that occurs without outside intervention is spontaneous . The reverse reaction is not spontaneous. Spontaneous process has a direction . Spontaneous Processes Spontaneous Processes General Chemistry II, Professor Maggie Ciszkowska General Chemistry II, Professor Maggie Ciszkowska
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A process that is spontaneous in one direction is not spontaneous in the opposite direction. The direction of a spontaneous process can depend on temperature: ice turning to water is spontaneous at T > 0 ° C, water turning to ice is spontaneous at T < 0 ° C. Reversible and Irreversible Processes A reversible process is one that can go back and forth between states along the same path. Spontaneous Processes Spontaneous Processes General Chemistry II, Professor Maggie Ciszkowska General Chemistry II, Professor Maggie Ciszkowska
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Reversible and Irreversible Processes Chemical systems in equilibrium are reversible . In any spontaneous process, the path between reactants and products is irreversible . Thermodynamics gives us the direction of a process. It cannot predict the speed at which the process will occur (chemical kinetics). Spontaneous Processes Spontaneous Processes General Chemistry II, Professor Maggie Ciszkowska General Chemistry II, Professor Maggie Ciszkowska
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The Spontaneous Expansion of a Gas Why does the gas expand? Entropy and the Entropy and the Second Law of Second Law of Thermodynamics Thermodynamics General Chemistry II, Professor Maggie Ciszkowska General Chemistry II, Professor Maggie Ciszkowska
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The Spontaneous Expansion of a Gas When there are many molecules, it is much more probable that the molecules will distribute among to the two flasks than all remain in only one flask. Entropy and the Second Law of Thermodynamics Entropy and the Second Law of Thermodynamics General Chemistry II, Professor Maggie Ciszkowska General Chemistry II, Professor Maggie Ciszkowska
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Entropy , S , is a measure of the disorder of a system. Spontaneous reactions proceed to lower energy or higher entropy . Entropy and the Second Law of Thermodynamics Entropy and the Second Law of Thermodynamics General Chemistry II, Professor Maggie Ciszkowska General Chemistry II, Professor Maggie Ciszkowska
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In ice, the molecules are very well ordered because of the H-bonds. Therefore, ice has a low entropy. As ice melts, the intermolecular forces are broken (requires energy), but the order is interrupted (so entropy increases).
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This note was uploaded on 04/08/2008 for the course CHEM 1.1 taught by Professor Ciszkowska during the Spring '08 term at CUNY Brooklyn.

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chem 1.1 chapter 19 - Thermodynamics: Entropy and Free...

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