• Rate of a reaction: change in concentration of reactants or products per unit time
  • Activation energy: minimum energy colliding particles must possess for a successful collision to take place
  • Catalysis: acceleration of a chemical reaction by catalyst


Effect of Concentration Changes

  • Increasing conc. of reactants increases rate of reaction: more particles per unit volume, collision rate between reacting particles increases,  rate of successful collision increases, resulting in increased rate of reaction.


Maxwell-Boltzmann Theory

  • Explains effect of temp. & catalyst on rate of reaction
  • Based on distribution of energy among reacting molecules under different conditions

Effect of Temperature

  • Number of collisions and chance of success will increase


Effect of Catalyst

  • Catalyst: a substance that increases rate of reaction but remains chemically unchanged itself at the end
  • Does not alter the chemical composition of substances and only lowers the activation energy
  • It provides a new route or mechanism to follow for reactants that requires less energy

  • Curve unchanged, only activation energy changes
  • Homogeneous catalysts: reactant and catalyst are in the same physical state
  • Heterogeneous catalysts: reactant and catalyst are in different physical states
  • Enzymes: a protein molecule that is a biological catalyst. Most are specific to a substrate & function as lock-key

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