Rates of reaction

• Rate of reaction= amount of reactant used or product formed/ time
• Reaction between marble chips and hydrochloric acid

  Calcium carbonate + hydrochloric acid -> Calcium chloride + water + carbon dioxide
• Marble chips, calcium carbonate (CaCO3) react with hydrochloric acid (HCl) to produce carbon dioxide gas
• Calcium chloride solution is also formed
• cotton wool


  • Allows carbon dioxide to escape, but stops any acid from spraying out
• Measuring change in mass of carbon dioxide

  1. Measure mass of carbon dioxide lost at intervals

  2. Plot a graph
• Graph becomes horizontal


  No more carbon dioxide is being produced, the reaction has stopped
• Graph is getting less steep


  The reaction is slowing down
• Graph is very steep


  Lots of carbon dioxide is being produced
• Catalyst


  • Increases the rate of a reaction
• Increasing the surface area of a solid

  • Increases the rate of a reaction
• Increasing the concentration of a solution


  • Increases the rate of a reaction
• Increasing the pressure of a gas


  • Increases the rate of a reaction
• Increasing the temperature


  • Increases the rate of a reaction
• Using a catalyst


  • Increases the rate of a reaction
• A catalyst is something that speeds up the rate of reaction without being used up itself
• Effects of changes in surface area, concentration, pressure, and temperature on a reaction

  1. Increasing surface area of solid:

  2. More particles exposed

  3. More frequent collisions

  4. Increase rate of reaction

  5. Increasing concentration of solution or pressure of gas:

  6. More particles in same space

  7. More frequent collisions

  8. Increase rate of reaction

  9. Increasing temperature:

  10. Particles have more kinetic energy

  11. More frequent collisions

  12. Higher proportion of successful collisions (collision energy greater than or equal to activation energy)

  13. Increase rate of reaction
• A reaction happens when particles collide successfully
• A catalyst works by providing an alternative route with lower activation energy
• Oxygen is made in the lab from hydrogen peroxide using manganese oxide as a catalyst
• The equation for this reaction is 2H₂O₂ → 2H₂O + O₂
• Different catalysts are used to find out which is the most effective at decomposing hydrogen peroxide