C8

• rate of reaction = products formed OR reactants used ÷ time taken
• Factors affecting RoR:

  • temperature (inc = inc in rate)
  • surface area (inc = inc in rate)
  • concentration/pressure (inc = inc in rate)
  • catalyst:
  • lowers activation energy
  • to create a new pathway
  • and more successful collisions
• Equilibrium = when forward and backward reaction even out/are at same speed
• Equilibrium

  • can only be in closed systems
  • concentrations of reactions will be constant but NOT equal
• Factors effecting equilibrium:

  • heating/cooling
  • pressure
  • concentration
  • catalyst has NO effect
• Le Chatilier’s Principle:

  if you change conditions of a reversible reaction, equilibrium will shift to counteract the change
• one reaction will be exothermic and the other endothermic

  • if temp is inc, equilibrium will shift to endo
  • if pressure is inc, equilibrium will shift to side with less molecules
• REQUIRED PRACTICAL ON CONCENTRATION

  • investigate effect of changing concentration
  • marble chips and HCl
  • change concentration but NOT volume of HCl
  • CO2 given off
  • measure change in mass of marble chips during reaction
• REQUIRED PRACTICAL DISAPPEARING CROSS (1)

  • using measuring cylinder, put 10cm³ of solution into conical flask and dilute with 40cm³ of water
  • place flask on black cross on paper
  • put 10cm³ of acid into small measuring cylinder
  • slowly swirl as you tip acid into flask and start stopwatch at the same time
  • stop stopwatch when you see cross disappear
• REQUIRED PRACTICAL DISAPPEARING CROSS (2)

  • record time in s on results table
  • repeat but with different measurements of solution and water (as solution inc, water dec)
  • plot line graph - concentration of solution as x axis and time for cross to disappear as y axis
  • equation: Na2S2O3 + HCl → NaCl + H2O + S + SO2 (S as precipitate)