Kinetics

• Describe the collision theory

  Chemical reactions occur when particles collide

  For a reaction to occur, the particles must have energy greater than or equal to the activation energy of the reaction

  Particle orientation must be correct too
• define rate or reaction

  the change in concentration of a substance in unit time

  moldm-3 s-1
• describe how the concentration affects the rate of reaction

  there are more particles in a given volume, so a higher frequency of successful collisions

  increased likelihood of collisions
• describe how the pressure affects the rate of reaction

  more particles in a given volume, with an increased likelihood of collisions

  so a higher frequency of successful collisions
• describe how the surface area affects the rate of reaction

  more space for reactants to collide with the molecules

  so a higher frequency of successful collisions
• Describe how the presence of a catalyst affects the rate of reaction

  Increases the rate of reaction without getting used up

  By providing an alternative route with a lower activation energy
• what is the maxwell boltzmann distribution curve?

  due to many collisions taking place, theres a distribution of energies and velocities

  area under the curve is a measure of number of particles
• What are the 3 major assumptions about the maxwell Boltzmann distribution curve?

  Gas molecules have negligible size compared with the container

  Collisions between molecules and container walls are elastic, so no energy is lost/gained when colliding

  Molecules don’t interact with each other
• describe how the curve shifts when the temperature increases

  shifts to higher energies

  curve gets broader and flatter due to a greater spread of values

  area under the curve stays constant - same number of particles

  a small rise in temperature leads to a large increase in rate because much higher number of particles have energy greater than or equal to Ea

  
• describe how the curve shifts when the temperature decreases

  curve gets narrower and more pointed due to a smaller spread of values

  area under curve stays constant
• Describe how the curve shifts when a catalyst is added

  Lowering the activation energy moves it to the left, resulting in a greater area under the curve - and more particles have energy greater than or equal to the activation energy

  Leading to a higher frequency of successful collisions

  Curve stays the same