AP Chemistry Unit 5.4 & 5.7 Elementary Reactions

Reaction Mechanisms

  • A chemical equation does not tell us how reactants become products
    • Simply a summary of the overall process
  • Elementary steps: series of steps by which a chemical reaction occurs
    • Cancel out identical species on opposite sides of the arrows in elementary steps to find overall balanced reaction
    • Elementary reactions involving the simultaneous collision of three or more particles are rare
      • Bcuz is unlikely that the collision will have sufficient energy and orientation for reaction to occur
  • Molecularity: refers to the number of moles that are reacting
  • Intermediate: something that is a product first in one elementary step and becomes a reactant in another
  • Catalyst: something that is a reactant first in one elementary step and becomes a product in another

  • Writing Rate Law Trick: can use the coefficient from the elementary step and turn it into the exponent for the rate law
    • Rate laws can only be determined in this manner for elementary steps!
  • The rate law for the slow rate determining step is the rate law for the entire overall balanced reaction
    • As long as the slow step is the first elementary step!
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