Kinetics

• What factors affect the rate of chemical reactions?

  Temperature, concentration, pressure, surface area, catalyst
• How does increasing temperature affect reaction rates?

  • Increases speed of particles
  • Increases energy and number of collisions
• How does increasing concentration affect reaction rates?

  • More particles in a given volume
  • Increases likelihood of collisions
• How does increasing pressure affect reaction rates?

  • Increases number of particles in a volume
  • Makes collisions more likely
• How does increasing surface area affect reaction rates?

  • More particles available to collide
  • Increases number of reaction sites
• What is a catalyst?

  A substance that changes reaction rate
• What is activation energy?

  The minimum energy needed to start a reaction
• What is the transition state?

  The intermediate complex during a reaction
• What does Ea represent?

  Activation energy
• What does the area to the right of Ea represent?

  Particles with enough energy to react
• What happens to the Maxwell-Boltzmann curve at higher temperatures?

  • Peak is lower and moves to the right
  • More particles have high energy
  • Total area under the curve remains the same
• What does the Maxwell-Boltzmann graph show at higher temperatures?

  More molecules have energy greater than Ea
• What is the most probable energy in a Maxwell-Boltzmann distribution?

  The peak of the curve
• Why should the energy distribution never meet the x-axis?

  There is no maximum energy for molecules
• What do catalysts do in a chemical reaction?

  Provide a pathway with lower activation energy
• Why are catalytic converters honeycomb in shape?

  • Increases surface area
  • Maximizes efficiency of the catalyst
• How do reactions take place on a catalyst?

  1. Gases form weak bonds with catalyst
  2. Gases held in position to react
  3. Products break away
• What happens to the Maxwell-Boltzmann graph at higher concentration?

  • Shape of the curve does not change
  • Area under the curve increases
  • More particles present but not a higher proportion with energy greater than Ea
• Why do most collisions not lead to a reaction?

  Not sufficient energy or correct orientation
• What happens to a Maxwell-Boltzmann graph when a catalyst is added?

  Activation energy is lowered and moves to the left
• What is a catalyst?

  A substance that speeds up a reaction by providing an alternative reaction pathway with a lower activation energy that isn't used up or changed itself
• Do catalysts affect enthalpy change?

  No
• What metals are used in a catalytic converter?

  Rhodium and platinum