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Chemical Kinetics Diagrams of Energy Changes in Reactions
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What happens to Energy During a Reaction? Exothermic vs Endothermic Does it increase or decrease uniformly? Potential Energy Diagram:
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Potential Energy Diagram: Forward Reaction Potential Energy (KJ) Reaction Coordinate H 2 + I 2 2HI Refer to the next slide for the key.
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Parts of a Potential Energy Diagram A.Potential Energy of the Reactants B.Potential Energy of the Products C.Activated Complex = D. Potential Energy of the Activated Complex E. Activation Energy (E A ) = F. Heat of Reaction (∆H) = Is this reaction exothermic or endothermic?
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Potential Energy Diagram: Reverse Reaction Potential Energy (KJ) Reaction Coordinate H 2 + I 2 2HI Refer to the previous slide for the key.
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Potential Energy Diagram: FWD: _______________ REV: _______________ Potential Energy (KJ) Reaction Coordinate Complete the PE diagram by drawing arrows to indicate the appropriate factors.
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Effect of a Catalyst: Potential Energy (KJ) Reaction Coordinate http://www.sasked.gov.sk.ca/branches/elearning/tsl/resources/subject_area/science/chem_30_resources/lesson_3/action_of_catalysts.shtml http://www.sasked.gov.sk.ca/branches/elearning/tsl/resources/subject_area/science/chem_30_resources/lesson_3/heat_of_reaction_and_catalysts.shtml http://www.sasked.gov.sk.ca/branches/elearning/tsl/resources/subject_area/science/chem_30_resources/lesson_3/reaction_mechanisms.shtml
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Things to Consider Is the forward reaction exothermic or endothermic? Reverse reaction? Is ∆H positive or negative for the forward reaction? Reverse reaction? What factors are the same in the forward and reverse reactions and what factors are different? How does a catalyst affect the forward and reverse reactions? On what factors does the catalyst have an effect and on what factors does it not have an effect?
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A + B C + 30 KJ E A = 20 KJ Potential Energy (KJ) Reaction Coordinate
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Enthalpy = Energy There is a tendency in nature to change to a state of lower energy (enthalpy). _________________ reactions result in a lower state of energy for the products than the reactants. _________________ reactions require less activation energy and therefore occur more easily than _______________ reactions. For the reasons above, _________________ reactions are said to be ___________________. Table I: Heats of Reaction at Standard Pressure and Room Temp. + Δ H = _________________________________ - Δ H = _________________________________
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Entropy = Disorder There is a tendency in nature to change to a state of greater disorder (higher entropy). It is expected that systems will go from a state of _____________ entropy to a state of _____________ entropy and not the other way around. Think of your bedroom, or book bag, or the desk in front of this class. In going from solid liquid gas, is entropy increasing or decreasing? In going from solid aqueous, is entropy increasing or decreasing? In a chemical reaction, the side with the greatest number of particles has the ____________entropy.
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Homework Potential Energy Diagrams: Orange Book: Pg. 113-114, Q 11-17 *Pg. 121-122, Q 3, 6-12, 15-16 *Pg. 123, Q 24, 38, 39 Enthalpy and Entropy: Orange Book: Pg. 119-120, Q 36-44 *Pg. 122, Q 14, 29, 30, 34 Equilibrium: Orange Book: Pg. 122-124, Q 13, 17, 20, 25-28, 31-33, 35, 36, 40 *Must do. Other HW questions are optional.
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