Kinetics 2010

Kinetics 2010 - Chemical Chemical Kinetics and Equilibrium...

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hemical inetics Chemical Kinetics and Equilibrium Part 1: Kinetics David A. Katz Department of Chemistry Pima Community College Tucson, AZ USA
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hemical Kinetics Chemical Kinetics The study of the rates of chemical reactions and how they occur. The conditions that affect the rate or speed at which reactions occur. The reaction mechanism ( how the reaction occurs at the atomic- molecular level).
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eaction Rates Reaction rate = change in Reaction Rates concentration of a reactant or roduct with time. product with time. concentration Rate= time Rate can be expressed as initial rate average rate instantaneous rate
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Determining a Reaction Rate
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actors Affecting Reaction Rates Factors Affecting Reaction Rates Physical State of the Reactants In order to react, molecules must come in contact with each other. The more homogeneous the mixture of actants the faster the molecules can reactants, the faster the molecules can react. aseous reactions are preferred Gaseous reactions are preferred Solutions are most convenient
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actors Affecting Reaction Rates Factors Affecting Reaction Rates oncentration of Reactants Concentration of Reactants As the concentration of reactants increases, so does the likelihood that reactant molecules will collide . Burning iron in air Burning iron in oxygen Burning an iron nail
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Lycopodium powder burning: a) In an evaporating dish b) In air
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actors Affecting Reaction Rates Factors Affecting Reaction Rates Temperature t higher temperatures, reactant At higher temperatures, reactant molecules have more kinetic energy, move faster, and collide more often and with greater energy.
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actors Affecting Reaction Rates Factors Affecting Reaction Rates atalysis Catalysis Catalysts speed up reactions by hanging the mechanism of the changing the mechanism of the reaction. Catalysts are not consumed during the course of the reaction. Negative catalysts (inhibitors) can be used to slow down the rate of a reaction.
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Collision Theory of Reaction Rates In a chemical reaction, bonds are broken and new bonds are formed. Molecules can only react if they ollide with each other collide with each other.
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Collision Theory of Reaction Rates The possible collisions for three sets of molecules at would result in that would result in a possible reaction
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Collision Theory of Reaction Rates For a collision to be effective (i.e., result in a reaction): Molecules must collide with the correct orientation (or alignment) There must be enough energy to overcome pulsions so molecules do not rebound repulsions so molecules do not rebound Bonds must break and new bonds formed.
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Collision Theory of Reaction Rates N O + N O 3 2 N O 2 “ neffective” Ineffective means that this has a lower probability of reacting.
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Activation Energy There is a minimum amount of energy required for reaction: the activation energy , E .
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This note was uploaded on 12/07/2011 for the course CHEM 152 taught by Professor Staff during the Spring '08 term at Pima CC.

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Kinetics 2010 - Chemical Chemical Kinetics and Equilibrium...

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