Redox Titration - Analysis of a Commercial Bleach

Lab report for determination of concentration of the active ingredient in commercial bleach, sodium hypochlorite, by the redox titrimetric analysis with sodium thiosulfate.

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Purpose
Objective of this experiment was to learn the concept and technique of redox titration through determination of sodium hypochlorite amount in a commercial bleach by reaction with sodium thiosulfate in the presence of iodide ions and starch. A solution of sodium thiosulfate of known concentration was added to the formed solution of triiodide ions using a burette in a titration procedure. The end point was observed through disappearance of the dark blue color of the starch-iodine complex.

Introduction
Oxidation and reduction reactions are defined as any reaction that involves transfer of electrons from one substance to another. Oxidation numbers of elements in the reaction are changed. The substance that donates electrons is oxidized in the process of oxidation. The substance that accepts electrons have a decrease in oxidation number and is reduced. In a redox reactions the total number of donated electrons must be equal to total number of accepted electrons....