Rates of Reaction

• what is the collision theory?

  chemical reactions can only take place when the reacting particles collide with eacohother. they need lots of energy
• define exothermic reaction


  energy that is released into the surroundings
• what is the activation energy?

  minimum amount of energy that the particles must have in order to react
• what happens when you increase the temp?

  • increasing temp increases the energy of the particles= more KE
  • the particles have more energy now so they move faster
  • they move faster so they collide more = overcome AC= more frequent successful collisions
• how does increasing surface area increase the rate of reaction?

  1. crushing up a soild increases the total surface area
  2. this allows more area for particles to move around
  3. this allows a greater number of collisions = more frequent successful collisions
• how does increasing concentration increase the rate of reaction?

  1. increasing conc will increase the no of particles present in a container
  2. reduces space for particles to move around
  3. increase the no of collisions= more frequent successful collisions
• how does increasing pressure increase the rate of reaction?

  1. increasing pressure= reduces the size of container
  2. the same number of particles will have less space to move around
  3. increases force of collision against container = more frequent successful collisions
• 4 factors affecting the rate of reaction?

  1/ temp

  2/ pressure

  3/ concentration

  4/ surface area
• what happens to the equilibrium if pressure increases?

  the position of the equlibrium shifts to the side with the smaller number of molecules (moles)
• what happens to the equlibrium if pressure decreases?

  the position of the equlibrium shifts to the side with the larger number of molecules
• what happens to the equilibrium if conc is increased or decreased?

  if one increases/decreases, the equlibrium will favour the opposite side to balance it
• what happens to the equlibrium if u increase the temp?

  if u increase the temp of the reaction, the equlibrium shifts to the endothermic side to reduce temp
• what happens to the equilibrium if u decrease the temp?

  the equilibrium shifts to the exothermic side to increase the temp
• typically what is the forwards reaction?


  exothermic
• typically what is the backwards reaction?

  endothermic
• what is the role of a catalyst?


  increases the rate of reaction by providing an alternative pathway for the reaction that has a lower AE
• what is an endothermic reaction?

  absorbs heat from its surroundings.
• why does the rate of reaction decrease?


  lots of the reactant molecules have already reacted and turned into product
• mean rate of reaction= quantity of product formed OR reactant used / time taken