Beng 130 Lecture 8

Beng 130 Lecture 8 - Free Energy and Phase Equilibria Free...

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Free energy and equilibrium Free energy and equilibrium Chemical potentials Chemical potentials – Partial Molar Free Energy Partial Molar Free Energy Standard states and activities of chemicals Standard states and activities of chemicals Molecular Physical Chemistry – Lecture 8 Reading: Reading: Gibbs Free Energy and Spontaneous Processes In living systems, the sum total of all the processes occurring can be spontaneous even if many of the individual steps taken by themselves are not. e.g. ADP + Pi Æ ATP is common in biochemical metabolism but in a solution of ADP and Pi, quantitative conversion does not occur spontaneously. Thermodynamics determines the extent to which reactions (like formation of ATP) are thermodynamically unfavorable and how such unfavorable steps can be combined with spontaneous reactions to make the entire reaction spontaneous. When is a process spontaneous? Free Energy –The Currency for Energy Transactions The role of thermodynamics in such problems is to determine the extent to which reactions like the formation of ATP are thermodynamically unfavorable and find out how such unfavorable steps can be combined with spontaneous favorable processes to make the total process spontaneous. Why can’s we use entropy maximum criteria? First biochemical reactions occur under constant T, P, etc. and the system is hardly isolated or definable! We need a currency for such energy transactions! - Gibbs and Helmholtz free energies Gibbs Free Energy and Spontaneous Processes Second law of thermodynamics: Entropy is not conserved. Entropy of the universe increases. Entropy of an isolated system increases in a spontaneous process: 0 ǻ S ǻ S ǻ S gs surroundin system total t . 0 ǻ
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Beng 130 Lecture 8 - Free Energy and Phase Equilibria Free...

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