Wednesday 3 June 2015

2.7.2c: carry out an iodine/thiosulfate titration, including calculation of the results and evaluation of the procedures involved, eg determination of the purity of potassium iodate(V) by liberation of iodine and titration with standard sodium thiosulfate solution

Titration to find the concentration of an iodine solution, using sodium thiosulfate of a known concentration

  • a known volume of oxidising agent (such as potassium iodate (V)) is reacted with iodide ions in excess potassium iodide solution to liberate iodine
    • IO3-(aq) + 5I-(aq) → 3I2(aq) + 3H2O(l)
  • the iodine formed is titrated with thiosulfate to determine the purity of the potassium iodate (V)
    • I2 + 2S2O32- → S4O62- + 2I-
  • starch is used as an indicator just before the end point to prevent a complex from forming (turns from blue/black to colourless)
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  1. alfachemistry16 March 2019 at 08:06

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