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Published byJasmin Small Modified over 6 years ago
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Redox titrations – iodine and thiosulfate
L.O.: Understand how to carry out redox titrations and carry out structured calculations involving MnO4- and I2/S2O32-
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2S2O32- → S4O62- +2e- I2 → I-
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Using iodine and thiosulfate to find out the concentration of an unknown OXIDISING agent
Iodine is reduced by thiosulfate ions into iodide ions in this reaction 2S2O32- (aq) + I2 (aq) 2I- (aq) + S4O62-(aq) A small amount of starch can be added to help identify the end point. Starch-iodine complex is dark/black.
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Uses of the iodine/thiosulfate redox reaction
Iodide ions are added to an oxidising agent which oxidises them into iodine You work out concentration of iodine by titrating the solution against a known number of moles of thiosulphate ions
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Work out the balanced equation for the oxidation of Iodide by bleach (ClO-)
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30. 00 cm3 of bleach was added to an excess of iodide ions
30.00 cm3 of bleach was added to an excess of iodide ions. The iodine formed was titrated against mol/dm3 solution of thiosulfate cm3 of thiosulfate was needed. Calculate concentration of Chlorate(I) ions in solution.
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