OZ 2

• Most collisions between particles do not lead to a reaction
• Maxwell Boltzmann distribution shows the energy distribution of gas particles, where particles have different speeds and kinetic energies
• Activation energy is the energy required for bonds to break and for particles to collide in a reaction
• Rate of reaction is the change of concentration or amount of a reactant or product per unit time
• Reactions with low activation energies require less energy to break bonds, while reactions with high activation energies require more energy
• Activation energy

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

  For a reaction to occur, particles must collide in the right direction and have the minimum amount of kinetic energy
• Effect of temperature on kinetic energy distribution

  Temperature affects the rate of reaction. Heating increases the kinetic energy of particles, leading to a larger proportion of molecules having energy greater than the activation energy. Cooling decreases the proportion of molecules with energy greater than the activation energy.
• Higher temperature results in more particles having energy greater than the activation energy, leading to a faster rate of reaction due to increased collisions and more energetic collisions.
• Graph of kinetic energy distribution

  Graph starts at zero zero, representing no particles with zero kinetic energy. Peaks initially and then slowly drags down towards the end. The area under the curve represents the total number of molecules. The peak represents the most likely energy of a particle in a sample. The area under the curve beyond the activation energy indicates the particles with enough energy to react.
• Maxwell Boltzmann distribution

  • Small increase in temperature leads to a large increase in rate due to more collisions and more energetic collisions
• Pressure affecting rate of reaction

  Increasing pressure leads to particles being closer together, more frequent collisions, and a higher chance of a reaction
• Catalyst

  • Increases the rate of reaction by providing an alternative pathway with lower activation energy
  • Chemically unchanged at the end of the reaction
  • Used to speed up specific reactions
  • Different catalysts used for different reactions
  • Can lower the temperature required for the reaction
• Heterogeneous catalyst

  • Solid catalyst with a large surface area that rapidly increases the rate of reactions
• Catalyst affecting rate of reaction

  Lowers the activation energy, providing an alternative pathway for the reaction to proceed with less energy required
• Concentration affecting rate of reaction

  Higher concentration leads to particles being closer together, more frequent collisions, and a higher chance of a reaction
• Homogeneous catalyst

  • Catalyst in the same phase as the reactants
• Catalyst


  • Zeolite
• Temperature, concentration, pressure affecting rate of reaction

  Small increase in temperature, concentration, pressure increases the rate of reaction
• Homogeneous catalysts

  Catalysts that are in the same phase as the reactants
• Measurement of reaction rates
• Homogeneous catalysts

  • Form an intermediate species during the reaction
  • Have two activation energies in the energy profile diagram
• Enzymes in body cells

  Biological catalysts that allow chemical reactions in the body to occur
• Aqueous catalysts

  • Sulfuric acid
• Homogeneous catalysts formation

  Combine with the reactants first, then release themselves to form the products while being reformed again
• Methods to measure reaction rates

  • Time for a precipitate to form
  • Amount of mass lost
  • Volume of gas produced
  • Change in temperature
  • Change in pH
  • Titration
• Homogeneous catalysts lower the activation energy of a reaction and are reformed during the process
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• Measuring pH via titration

  Change in pH allows us to use a pH meter to monitor the reaction progress. Samples are taken at intervals during the reaction. A quenching reagent is added to stop the reaction and freeze it at a specific moment in time. A titration is then performed to determine the amount of product produced in the reactor
• Rate of reaction can be determined by the gradient of a graph
• Calculating rate from a graph

  Rate can be found from the gradient of a graph. The change in Y over the change in X is calculated to determine the steepness of the graph. Tangents are used for curved graphs to find the rate at specific points
• Curved graphs require the use of tangents to calculate the rate of reaction at specific points