Redox Titrations Just as an acid can be used to find the concentration of a base (or vice versa) in an acid-base titration, a known concentration of an oxidising agent can be used to find the unknown concentration of a reducing agent (or vice versa). When dissolved in ethanol, polyiodide salts, NMe 4 .I(I 2 ) x or NMe 4 .I 2x+1 , are a source of 'free' iodine as in the equation: NMe 4 .I(I 2 ) x → NMe 4 + + I - + xI 2 An iodine / thiosulfate redox titration can be employed to determine the amount of I 2 released. The chemical equation for the iodine / thiosulfate titration is:
I 2 + 2S 2 O 3 2- → S 4 O 6 2- + 2I - 1. 1. - The oxidising agent in the titration is I 2 Correct! HintExplanation 2. 2. - The indicator used in this titration is starch Correct! HintExplanation 3. 3. -
The colour change indicating the end-point of the titration is from blue to colourless Correct! HintExplanation Using Titration Data In a redox analysis of a polyiodide salt by titration of the liberated iodine with shiosulfate, titration of 20.00 mL aliquots of a solution of the polyiodide salt (initial volume 100.0 mL) containing elemental iodine, yielded an average titre of 21.15 mL of 0.02000 M thiosulfate solution. NMe 4 .I(I 2 ) x → NMe 4 + + I - + xI 2 I 2 + 2S 2 O 3 2- → S 4 O 6 2- + 2I - 1.
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- Chemistry, 14.6 %, 0.02000 M, 0.3787 g