Rates of Reaction

• Sodium thiosulfate reacting with HCl

  1. Add sodium thiosulfate solution to a flask

  2. Place flask on a black cross

  3. Add HCl

  4. Time how long it takes for the cross to disappear

  5. Record the results

  6. Repeat with different concentrations
• Rate of reaction formula


  Mean rate of reaction = quantity of product formed / time taken
• Equilibrium


  When the forward reaction is equal to the backward reaction
• Reactions can only reach equilibrium in a closed system
• Increasing surface area of solid reactant

  Increases the rate of reaction
• Catalyst


  Speeds up the rate of a reaction without being used up
• Reversible reaction symbol


  Reaction going forwards and backwards
• Le Chatelier's Principle


  If the conditions are changed in a reversible reaction, the system will counteract that change (e.g. temperature, pressure, concentration)
• Marble chips and hydrochloric acid producing carbon dioxide

  1. Measure out the HCl

  2. Pour into a conical flask

  3. Measure out the marble chips

  4. Add to the flask and add the bung and delivery tube

  5. Start the stopwatch

  6. Collect the gas in the gas syringe, measure every 10s and write down the results
• The quicker the mass lost, the quicker the reaction
• A tangent on the graph shows how the reaction rate changes