required practical 7 - hydrogen peroxide and iodide ions

• what is this practical?

  measure the rate of reaction using an initial rate method.
• what's an example of a clock reaction?

  the reaction between hydrogen peroxide and iodide ions.
• what is added to what

  a solution of acidified hydrogen peroxide is added to the solution of sodium thiosulfate and iodine ions and a starch indicator
• what is the equation?

  H2O2(aq) +2H+(aq) +2I-(aq) --> I2(aq) + 2H20(l)
• what does the starch indicator show?

  the presence of iodine through the formation of a blue-black complex.
• what do we record the time for?

  the blue-black colour to appear in the reaction mixture.