C8 - Rates of Reaction

• Rate of Reaction:

  • Amount of product made in a certain time

  Or

  • Amount of reactant used up in a certain time

  
• How to measure how much product has been made or used up:

  • Add a gas syringe to the beaker and measure the volume of gas
  • Measure mass of gas whilst reacting to see how much product has been used up
  • Cotton wool is place in the tube to prevent loss of mass through evaporation
  • Disappearing cross experiment
  • Time taken for the colour change to prevent you from seeing the cross
• You can calculate the rate of reaction at any point of the reaction by drawing a tangent to the curve, and calculating the gradient of the tangent to find the rate of reaction
• Collision Theory - Reactions will only take place if our reactants react with enough energy and with correct orientation
• Ways to increase the rates of reaction

  • Increased temperature
  • Increased concentration
  • Increase surface area : volume ratio
• Using a catalyst to lower activation energy

  • Catalyst lowers activation energy
  • Less energy required to make the reaction happy
  • Benefits:
  • Catalyst isn't used up
  • Lower temperature to react a substance
  • Drawbacks
  • Catalysts are expensive and rare
  • Catalysts are only specific to one type of reaction each
• Reversible reaction - a reaction that can be reversed both ways
• Dynamic equilibrium is when the forward rate = the backward rate
• Le Chateliers Principle:

  • Try and counteract change
  • Increasing temperature
  • Increasing pressure
  • Increasing concentration