RP05 - Rate of Reaction

• What are three ways of measuring the rate of a reaction?

  Observe precipitate, measure mass, measure gas volume
• What are the methods to measure the rate of a reaction?

  • Observe how quickly a precipitate forms
  • Measure the change in mass
  • Measure the volume of gas given off
• How do you calculate the rate of reaction?

  Rate = product formed or reactant used / time
• How can you measure the rate of reaction if a precipitate is produced?

  Use a black cross and time its disappearance
• How can you measure the rate of reaction if colored reactants form a colorless solution?

  Time how long it takes to turn colorless
• Why is the precipitate rate experiment not very reliable?

  It is subjective; opinions may vary on timing
• How can you measure the rate of reaction when there is a change in mass?

  Use a mass balance and record at intervals
• What is the procedure to measure the rate of reaction when a gas is given off?

  Attach a gas syringe to a conical flask
• How can you find the rate of reaction after 30 seconds?

  Plot results, draw tangent, calculate gradient
• What are the units of rate of reaction when measuring a change in mass?

  g/s
• What are the units of rate of reaction when measuring gas volume?

  cm³/s
• How can you investigate how HCl concentration affects the rate of reaction with magnesium?

  • Place HCl in a conical flask
  • Add magnesium ribbon and fit bung with gas syringe
  • Record gas volume every 10 seconds
  • Repeat with different HCl concentrations
  • Compare rates for each concentration
• How can you investigate how sodium thiosulfate concentration affects the rate of reaction with HCl?

  • Add 30 cm³ sodium thiosulfate to a conical flask
  • Add 10 cm³ dilute HCl
  • Measure time for cross to disappear
  • Repeat three times for mean time
  • Test different concentrations of sodium thiosulfate