3.1.5 Kinetics

• rate of reaction - change in concentration of a reactant or product in a

  given period of time
• activation energy - minimum amount of energy which the reacting

  particles require for a successful collision
• catalyst - substance that increases the rate of a chemical reaction without being changed in chemical composition or amount
• Catalysts work by providing an alternative reaction route of lower activation energy
• why do most collisions not lead to a reaction?

  Not all the particles have greater or equal amount of energy to the activation energy
• Maxwell–Boltzmann distribution

  • lower temp
  • distributions moved to left
  • peak is higher
• Maxwell–Boltzmann

  • higher temp
  • distributions moved to right
  • lower peak
• Why does the Maxwell-Boltzmann curve start at zero?

  zero molecules have zero energy
• What is the effect of changes in pressure on collision frequency?

  if pressure increases, less time is taken to reach equilibrium

  -occurs at a faster rate

  - particles are closer together

  - more particles have energy that is greater or equal to activation energy

  - increased frequency of successful collisions

  - rate of reaction increases

  
  

  if pressure decreases, more time is taken to reach equilibrium

  -occurs at a slower rate

  - particles are not closer together

  - less particles have energy that is greater or equal to activation energy

  - less frequent successful collisions

  - rate of reaction decreases
• What is the effect of changes in concentration on collision frequency?

  if concentration increases, there are more particles within a given volume

  - particles are closer together

  - more frequent successful collisions

  - more particles have energy that is greater or equal to activation energy

  - rate of reaction increases

  
  

  if concentration decreases, there are less particles within a given volume

  - particles are not closer together

  - less frequent successful collisions

  - less particles have energy that is greater or equal to activation energy

  - rate of reaction decreases
• what does the area under the Maxwell- Boltzmann curve represent?


  area under curve = total number of gas particles
• What does the peak of the curve represent?

  -EMP

  - most probable energy thatmostof the particles have
• With use of the Maxwell-Boltzmann distribution, explain why a small temperature increase can lead to a large increase in rate?

  There is a larger area under the curve therefore more particles have energy that is greater or equal to the activation energy.

  Therefore, the frequency of successful collisions increases hence rate of reaction increases
• What is a catalyst?

  -substance that speeds up rate of reaction but is chemically unchanged

  
  

  - provides an alternative route that lowers activation energy
• With use of a Maxwell-Boltzmann distribution, explain how a catalyst increases the rate of a reaction involving a gas.

  catalyst speed up the rate of reaction by providing an alternative route with lower activation energy.

  
  

  - more particles have energy that is greater or equal to activation energy

  
  

  - rate of reaction increases