Iodometric assay for the determination of chlorine in a household bleach. An interactive lab experiment.
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In this simulated lab exercise, the procedure for determining chlorine in a household bleach using the iodometric method is explained in detail. Every step of the protocol is carried out, from the weighing and dissolution of sodium thiosulfate used as titrant, until the final calculation of the concentration (as g / L of active chlorine in the sample) using the data of five determinations. Chemical reactions that take place at different stages are presented, as well as the conversion relationships between the species involved in the analysis. The data are randomly generated and the concentration range of the bleach analysed sample is in the range 26-38 grams per liter of active chlorine. The standardization of thiosulfate is performed by means of three replicates, from which the average value of this parameter is obtained. In the sample analysis, the data are obtained from 1 experimental titration plus 4 random additional titrations. An outlier can appear. In this case, the user has to submit this value to the Dixon’s Q test of rejection. If the five determinations are statistically acceptable, the calculated average value of the chlorine content is given with the associated uncertainty.