lecnotes18 - MIT OpenCourseWare http:/ocw.mit.edu 5.111...

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MIT OpenCourseWare http://ocw.mit.edu 5.111 Principles of Chemical Science Fall 2008 For information about citing these materials or our Terms of Use, visit: http://ocw.mit.edu/terms .
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__________________________________________________________________________ ________________________________________________________________________________ 5.111 Lecture Summary #18 Reading for today: Section 7.16 – Free-Energy Changes in Biological Systems. Exam #2 coming up Topics: Thermodynamics I. Free energy of formation II. Effect of temperature on spontaneity III. Thermodynamics in biological systems A. ATP-coupled reactions B. Hydrogen bonding I. FREEE ENERGY OF FORMATION, G f (continued from Lecture #17) G f º is a measure of a compound’s stability relative to its elements. If G f º < 0, a compound is thermodynamically _________________ relative to its elements. If G f º > 0, a compound is thermodynamically _________________ relative to its elements. 6C(gr) + 3H 2 (g) C 6 H 6 (l) G f º = 124 kJ/mol C 6 H 6 (l) 6C(gr) + 3H 2 (g) Gº = –124 kJ/mol The reverse reaction spontaneous, but very, very slow! Free energy tells whether or not a reaction will happen spontaneously, but tells us ______________ about the rate of the reaction (for rate information we need kinetics). To calculate G° for a reaction… G r ° = Σ G f °(products) - Σ G f °(reactants) OR G r ° = H r ° – T S r ° II. EFFECT OF TEMPERATURE ON SPONTANEITY Consider the decomposition of sodium bicarbonate at 298 versus 450. K.
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This note was uploaded on 11/27/2011 for the course CHEMICAL E 20.410j taught by Professor Rogerd.kamm during the Spring '03 term at MIT.

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lecnotes18 - MIT OpenCourseWare http:/ocw.mit.edu 5.111...

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