Kinetics

• What must happen for a reaction to occur?

  Particles must collide with sufficient energy
• How is rate defined in kinetics?

  Change in concentration of a substance per unit time
• What is the formula for rate in a reaction?

  Rate = amount of reactant used / time
• What is required for a reaction to occur after a collision?

  Correct orientation and sufficient energy
• What is activation energy?

  Minimum amount of energy that particles need to react
• What happens to bonds during a reaction?

  Bonds stretch and break with energy
• What does the Maxwell-Boltzmann distribution illustrate?

  Energy distribution in gas particles
• What does the area under the Maxwell-Boltzmann curve represent?

  Total number of molecules
• What is the difference between most likely energy and mean energy in a sample?

  Most likely is the peak; mean is right of peak
• How does temperature affect the rate of reaction?

  Higher temperature increases kinetic energy
• What is the effect of increasing temperature on the Maxwell-Boltzmann distribution curve?

  Shifts to the right with a lower peak as more particles have energy greater than activation energy
• What happens when temperature is decreased in a reaction?

  Fewer molecules exceed activation energy
• Why does increasing temperature lead to faster reactions?

  More frequent and successful collisions occur
• How does pressure affect the rate of reaction?

  Higher pressure increases frequency of successful collisions
• How does concentration affect the rate of reaction?

  Higher concentration increases frequency of successful collisions
• What is a catalyst?

  Substance that speeds up the rate of a chemical reaction without being used up or chemically changed at the end of a reaction
• How do catalysts affect activation energy?

  They provide an alternative pathway with lower energy
• How does a catalyst shift the Maxwell-Boltzmann distribution curve?

  Shifts activation energy to the left as more particles will have energy greater than the activation energy
• How can reaction rates be measured experimentally?

  By timing precipitate formation or gas production
• How can the volume of gas produced be measured?

  Using a gas syringe over time
• What should be done when measuring gas volume in experiments?

  Repeat the experiment with different conditions
• How does the energy of products compare to reactants in an endothermic reaction?

  Products have higher energy than reactants
• What happens to the rate of reaction as reactants are used up?

  The rate decreases over time
• Why are catalysts useful in industry?

  They reduce costs by lowering energy needs
• What factors affect the rate of reaction?

  • Concentration of solution/pressure of gas
  • Catalyst presence
  • Temperature
  • Surface area
• How does temperature affect the rate of reaction?

  • Higher temperatures increase kinetic energy
  • More particles exceed activation energy
  • Results in more frequent successful collisions
• How does surface area influence reaction rates?

  • Increasing surface area exposes more particles
  • More particles available to collide
  • Results in more frequent successful collisions
• Why does the energy distribution never meet the x axis on the Maxwell Boltzmann distribution graph?

  No maximum energy for molecules
• Why does the Maxwell Boltzmann distribution curve not start at 0?

  No molecules have 0 energy
• What is the effect of increasing concentration/pressure on the Maxwell-Boltzmann distribution curve?

  Curves will be higher and area under the curves will be greater because there are more particles

  Shape of energy distribution curve does not change
• What is the effect of increasing surface area on the Maxwell-Boltzmann distribution curve?

  Doesn't change Maxwell Boltzmann curve as no effect on energy of particles
• How does the energy of reactants compare to the products in an exothermic reaction?

  Reactants have higher energy than products