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Rate of Reaction

Rate of Reaction. Five Factors that affect the Rate of Reaction. Learning Goals be able to explain, using the collision theory, how the 5 factors affect reaction rates. Reaction Rates. Chemical Reactions occur only when reactants collide: In the proper orientation for bonds to form

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Rate of Reaction

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  1. Rate of Reaction Five Factors that affect the Rate of Reaction • Learning Goals • be able to explain, using the collision theory, how the 5 factors affect reaction rates

  2. Reaction Rates Chemical Reactions occur only when reactants collide: • In the proper orientation for bonds to form • With enough kinetic energy (break old bonds and form new bonds) – reach Activation Energy EFFECTIVE INEFFECTIVEcollisions result in an elastic collision but no chemical rxn.

  3. Activation Energy (Ea) • Two main purposes: • Used to overcome the electrostatic repulsive forces between colliding reactants • Used to weaken the bonds of the reactants The minimum amount of energy that a reactant must have for a collision to be effective ‘Barrier’ to the reaction

  4. Activation Complex (or Transition State) • New bonds are made before old bonds are broken • The activation complex is an unstable “Super Molecule” consisting of all reactants bonded together • Is very unstable with a high potential energy (the maximum in the change)

  5. Recall

  6. Five Factors that affect theRate of Reaction • Temperature • Concentration/Pressure • Surface Area • Catalysts/Inhibitors • Chemical Nature of Reactants

  7. Temperature • As the temperature increases the average Kinetic Energy increases. • More effective collisions = higher reaction rate http://comp.uark.edu/~jgeabana/mol_dyn/KinThI.html http://www.chm.davidson.edu/vce/kinetics/ReactionRates.html

  8. Temperature As the temperature is increased from T1 to T2 the KE of the particles increases and more particles achieve the activation energy F REACTION

  9. Concentration & Surface Area • Concentration: As the number of particles increases the number of collisions increases (constant volume). • Surface Area: the more space for particles to react, the more likely they will collide.

  10. Catalysts • reduce the activation energy of the reaction. • Lower the activation energy = more particles will have the required amount of energy to react.

  11. Nature of the Reactants • Rate depends on reactivity of reactants. Ex. Au <<< less reactive than Na.

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