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• What is a 'clock reaction'?

  A reaction with a quick concentration change
• What method can be used to find the order of reaction with respect to iodide ions in the iodine clock reaction?

  1. Mix potassium iodide, sodium thiosulfate, and starch solutions in a conical flask.
  2. Add potassium peroxodisulphate and start the timer.
  3. Record the time taken for the solution to turn blue-black.
  4. Repeat with varying concentrations of KI.
• How can the order of a reactant be deduced from the rate of reaction?

  By analyzing rate changes and concentrations
• What are the word and chemical equations for the reaction between potassium iodide and potassium peroxodisulphate?

  • Word equation: Potassium iodide + potassium peroxodisulphate → potassium sulphate + iodine
  • Chemical equation: $K_2S_2O_8 +$$2KI → 2K_2SO_4 +$$I_2$
• What equation links moles, volume, and concentration?

  Moles = volume x concentration
• How can the initial rate be calculated for an iodine clock reaction?

  Initial rate = moles of iodine / time
• What are two possible sources of error in an iodine clock experiment?

  • Inaccurate timing of the appearance of blue color.
  • Adding starch increases the volume, affecting concentrations.
• What are some control variables for the iodine clock experiment?

  • Total volume of reactants
  • Volume of starch and thiosulfate used
  • Concentrations of all reagents (except KI)
  • Temperature
• What is the rate equation for the reaction between iodide ions and peroxodisulphate ions?

  Rate = k [I-] [S2O8^2-]
• What is the overall order of the reaction between iodide ions and peroxodisulphate ions?

  2