Analysis of NaOCl Solution

OCr ions oxidise iodide in acid solution, to iodine which is titrated with standardised thiosulphate solution. 

Pipette 25.0 cm of the commercial NaOCl solution (Freshly supplied) into a 250 cm conical flask and add 50 cm water and 2 g KI, acidify with 10 cm glacial acetic acid and titrate the liberated iodine with standardised 0.05 M thiosulphate solution using starch indicator (Sec.7.3.1). Repeat to obtain concordant results. Calculate, from the average titre, [OCf] in mol dm . 

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