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iron thing chemisty lab

iron thing chemisty lab - BROOKLYN COLLEGE Department of...

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FeO.doc mc 11/18/98 BROOKLYN COLLEGE Department of Chemistry Chemistry 41 Redox Titration with Potassium Permanganate. Determination of Iron in an Ore. In this experiment, the percentage of iron in an unknown iron oxide sample is determined by titration with a standard solution of potassium permanganate. Read Section 17C-1, pp 366-370, in the textbook for background and Section 36E, pp 833-838, for procedures before starting this experiment. Success in this analysis requires careful preparation and attention to detail. Prepare a summary of the procedures in your notebook before coming to lab. The overall reaction is: MnO 4 - + 8 H + + 5 Fe 2+ Mn 2+ + 5 Fe 3+ + 4 H 2 O To ensure that all of the iron in the unknown is in the Fe 2+ state prior to titration, the unknown is treated with tin(II) chloride, which reduces any small amount of Fe 3+ that might be present: Sn 2+ + 2 Fe 3+ Sn 4+ + 2 Fe 2+ The excess Sn 2+ is then removed by reaction with mercury(II) chloride, which produces insoluble mercury(I) chloride: Sn 2+ + 2 HgCl 2 Sn 4+ + Hg 2 Cl 2 (s) + 2 Cl - The potassium permanganate is previously standardized against sodium oxalate in acid solution: 2 MnO 4 - + 5 H 2 C 2 O 4 + 6 H + 2 Mn 2+ + 10 CO 2 + 8 H 2 O Potassium permanganate acts as its own indicator both in the standardization and in the iron determination. Preparation: Prepare the KMnO 4 solution and dry the sodium oxalate prior to the day you want to standardize the permanganate solution. The permanganate solution has to cool and stand overnight before it can be filtered to remove MnO 2 . Dry the iron oxide unknown in advance as well.
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FeO.doc mc 11/18/98 Experimental procedure consists of three steps: (see following pages for details) Preparation of 0.02 M potassium permanganate: Section 36E-1. Use one of the large beakers and the filter crucibles that are available in the lab for this experiment. Clean and return these as quickly as possible. We use a dilute solution of sodium bisulfite (NaHSO 3 ) for removing the MnO 2 stains on the glassware.
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