# 1101 - CHAPTER 9: Reaction Energetics Thermodynamics the...

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Section 9.1 CHAPTER 9: Reaction Energetics Thermodynamics- Kinetics- the study of energy and chemical reactions ( energy) deals with start and finish only (reactants and products), not the path can predict if a reaction “should” happen (is favorable) the study of the rates and mechanisms of chemical reactions deals with the path of the reaction and how fast or slow can predict if a reaction will happen in a reasonable amount of time Thermodynamics + Kinetics = Energetics

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Section 9.1 Thermodynamics Consider the energy change due to a chemical reaction. 1 Law of Thermodynamics- energy is neither created nor destroyed. (So energy can be converted or moved.) energy = E final - E initial If E < 0 (neg) E i > E f energy is released If E > 0 (pos) E i < E f energy is added
Section 9.1 Thermodynamics Universe = system + surroundings what you’re studying everything else E universe = E system + E surrondings = 0 E sys = – E sur Anything that happens to the system, the opposite happens to the surroundings. Ex. If the system gives off heat, the surroundings gains heat.

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Section 9.1 Thermodynamics Energy = heat (q) and work (w) E = q + w The sign on q and w indicates the flow from sys to sur. q > 0 heat absorbed by the system- “ endothermic q < 0 heat released by the system- “ exothermic w > 0 work done on the system w < 0 work done by the system
If 200 KJ of work are done on a system and 20 KJ of heat are given off, … What is the net energy change in the system? Is this change endothermic or exothermic? What is the net energy change in the surroundings? E sys = q + w E sys = -20 KJ + 200 KJ E sys = 180 KJ E sys > 0 So endothermic E sys = - E sur So E sur = -180 KJ

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Section 9.2 Enthalpy Enthalpy - the heat of a reaction at constant pressure ( H ) Enthalpy (H, heat) reactants products reactants products +heat H>0 endothermic reactants + heat products –heat H<0 exothermic reactants products + heat
Section 9.2 Standard State By definition, the “standard state” is the

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## This note was uploaded on 06/14/2009 for the course CH 101 taught by Professor Bigham during the Spring '08 term at N.C. State.

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1101 - CHAPTER 9: Reaction Energetics Thermodynamics the...

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