collision theory - factors affecting rate of rxn

Cards (12)

  • Reaction rate: the change in concentration of a reactant or product in a certain amount of time (mol/L/sec)
  • Collision theory: in order for a reaction to occur, reactant particles must collide. Collisions between particles will
    result in a chemical reaction if they are EFFECTIVE COLLISIONS
  • Kinetics: a branch of Chemistry that studies the rate or speed of chemical reactions and explain the collision theory
  • COLLISIONS are EFFECTIVE if particles collide with
    • correct/proper orientation AND
    • sufficient/proper/enough energy
  • The greater the number of collison, the higher the chance/probability of effective collisions.
    The greater the rate/frequency/number of EFFECTIVE COLLISIONS, the faster the rate of the reaction.
  • lonic vs covalent compounds.
    lonic: fast (almost instantaneous)
    • Why? no bond breaking is required
    Covalent (Molecular) substances: slower reactions.
    • Why? Require the breaking of strong covalent bonds
  • Phase/State of Matter
    • Gases (fast) > Liquids/aqueous (fast/slow)> Solids (slow)
    • Why? It takes energy to separate the particles from each other
  • Concentration
    • the concentration/amount of particles increases, the rate of reaction increases
    • why? more reacting particles/concentration increase frequency # of effective collisions & amount of collisions
  • Temperature
    • Temp. of particles increases, rate of reaction increases too
    • Why? Increases kinetic energy (KE) ----> particle movement faster ---> more particles will have sufficient energy during collisions ----> increases the amount/frequency of effective Collisions
  • Pressure
    • A change in pressure will affect the rate of a reaction when one or more reactants is a GAS.
    • Increasing pressure for a gas increases the rate of reaction
    • Why? When pressure increases, particles are more closer together, resulting in more collisions, which leads to the higher frequency of effective collisions.
  • Surface Area
    • amount of exposed area of a set mass of a solid substance
    • Big piece= low surface area.
    • Smaller pieces(example: crushing to powder)= more Surface area.
    • Increasing the surface area for a solid increases the rate of reaction
    • Why? It pieces split more, the surface area will increase. That would result in more pieces or particles, increasing the amount of collisions which increases the frequency of effective collisions
  • CATALYST: substance that is added to a chemical reaction. Adding a catalyst - increases reaction rate
    without being used up itself. (example - enzymes in the body)
    How? Lowers the activation energy; Provides a lower activation energy (alternate) pathway for a reaction to occur.
    Activation Energy: Energy needed to start a chemical reaction