Lec-09-Chap13-1-Complete

Lec-09-Chap13-1-Complete - Lec-09-Chap13-1-Complete Lec-09...

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Lec-09-Chap13-1-Complete 9/23/2011 Directionality of Chemical Reactions Entropy Changes. 3 rd Principle. Standard Molar Entropies. 2 nd Principle 1 Lec-09: Thermodynamics: Spontaneous Processes. Entropy and Free Energy Chapter 13 1 Room Assignments Solar ID Room 000000000 – 107757371 Javits 100 Main Floor 107757372 – 999999999 Javits 100 Balcony Dependence of the rate constant with temperature The Arrhenius Equation More energy is available to the reaction system as the temperature increases. E a is the activation energy (units of energy, kJ mol –1 ) R is the gas constant (kJ K –1 mol –1 ) T is the temperature (K) 2   frequency factor (same u rate nits constant as ) a k E RT A e kT This leads to a temperature dependence of the rate constant . Experimentally Arrhenius found:
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Lec-09-Chap13-1-Complete 9/23/2011 Directionality of Chemical Reactions Entropy Changes. 3 rd Principle. Standard Molar Entropies. 2 nd Principle 2 Dependence of the rate constant with the temperature Potential Energy Reaction Progress R P E R E P E af E ab Δ E af ab E EE  forward reaction reac pro t ds ants uct Activation energy for the forward reaction reverse reaction r pr ea oducts ctants Activation energy for the reverse reaction 3 Elementary Reactions       rate constant A r te B a mn tt t k The rate law , frequently of the form reflects instead the detailed series of elementary reaction steps by which the chemical reaction proceeds . 4 A valid reaction mechanism should: Consist of a series of unimolecular and bimolecular elementary reactions. Consist of reaction steps that sum to the overall reaction equation. Correctly predict the experimental rate law.
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Lec-09-Chap13-1-Complete 9/23/2011 Directionality of Chemical Reactions Entropy Changes. 3 rd Principle. Standard Molar Entropies. 2 nd Principle 3 There are two only two important types of elementary reactions: Elementary Reactions - continued a different Unimolecula partic the structure of rearranges to produce or . r : a molecu le or particl ion A le B es (atoms, molecules, or ions) react with each other and yiel prod ucts A Bimolecular: BC two p articles AB d C CD   rate A k    rate k 5 Mechanism with a Slow Initial Step       22 2 2NO g F g 2NO F g  6     1 2 2 2 2 slo NO F N NO w fa F F F + t O + s F k k  The slowest elementary process in a sequence is called the rate determining step .
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Lec-09-Chap13-1-Complete - Lec-09-Chap13-1-Complete Lec-09...

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