Kinetics

• Why does a small increase in temperature causes a large increase in the rate of reaction

  • Many more molecules have energy greater than or equal to the activation energy
  • so greater frequency of successful collisions
• Maxwell-Boltzmann distribution curve

  • y axis: number of molecules
  • the curve starts at the origin because there are no molecules with no energy
  • X = most probable energy

  
• What do Maxwell-Boltzmann distributions

  The distribution of the energies of all the particles in a sample of gas
• What does the shaded area on the following Maxwell-Boltzmann distribution represent?

  Particles with energy greater than or equal to the activation energy

  
• What does the area under the curve in a Maxwell-Boltzmann distribution represent?

  total number of particles in the sample
• A: Mean energy

  B: Activation energy

  C: Most probable energy

  
• The graph represents the reaction at a higher temperature

  
• Explain the distribution graph at a higher temperature

  • the peak of the distribution shifts right, because the most probable energy of particles has increased
  • The peak of the curve becomes lower and wider because the total area under the curve must remains the same
• The distribution graph for a reaction at a lower temperature

  
• Distribution curve at lower temperature

  the most probable energy of particles decreases, so the peak of the curve shifts left.

  The height of the peak of the curve increases and it becomes narrower because the total area under the curve must stay the same.
• distrubution curve of a reaction with a higher concentration

  
• distribution curve of a reaction with a decreased concentration

  the peak will become lower

  the curve will remain the same
• Why must distribution curves not touch the x-axis?

  A very small number of particles have extremely high energy, beyond the end of the x-axis
• distribution curves at a lower temperature

  • The number of particles with Emp​ will increase
  • The value of Emp​ will decrease
• Define catalyst


  a substance that increases the rate of a reaction without being used up
• Catalysts increase the proportion of collisions that are successful
• How do catalysts work?

  Catalysts provide an alternative pathway that lowers the activation energy which increases the rate of reaction
• Define activation energy

  the minimum energy required for a reaction to take place
• total number of molecules increases

  the value of the most probable energy stays the same