A Level Chemistry - Kinetics

• Rate of reaction


  The change in concentration or the amount of a reactant or product per unit time
• Particles are constantly moving and colliding, but most collisions do not lead to a reaction
• Activation energy


  The minimum amount of energy required for a reaction to occur
• Activation energy


  • It is the difference between the reactants and the top of the reaction profile line
  • Reactions with low activation energy need less energy to break them
• Maxwell-Boltzmann distribution


  Shows the energy in gas particles, with the peak representing the most likely energy and the mean slightly to the right
• Increasing temperature


  Increases the proportion of particles with energy greater than the activation energy
• Decreasing temperature


  Decreases the proportion of particles with energy greater than the activation energy
• Effects on rate of reaction

  • Increased temperature leads to faster, more frequent and more energetic collisions
  • Increased pressure or concentration brings particles closer together, increasing collision frequency
  • Catalysts provide an alternative pathway with lower activation energy
• Measuring rate of reaction

  1. Measuring time for precipitate formation

  2. Measuring mass loss due to gas production

  3. Measuring volume of gas produced over time
• Catalysts remain chemically unchanged at the end of the reaction
• Order of reaction refers to the power to which concentrations are raised in the rate law equation