S117LabLectureRedoxdeterminationofIron_001

S117LabLectureRedoxdeterminationofIron_001 - Redox...

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Redox determination of Iron The purpose of this lab is to teach you about: Redox chemistry Quantitative analysis Error propagation “Theory” behind the lab Iron commonly exists in the +2 and +3 oxidation states. FeO Fe 2 O 3 If we want to determine the total iron content in a sample how do we do it?
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1. dissolution of the sample Fe compounds are often insoluble in water They will dissolve in hot, concentrated HCl. Silica which does not dissolve in hot, concentrated HCl will appear as a white residue. 2. quantitative conversion of iron(III) to iron(II) with a suitable reducing agent 2Fe 3+ + SnCl 4 2 + 2Cl 2Fe 2+ + SnCl 6 2 Chloride complexes of Fe(III) are yellow while complexes of Fe(II) are colorless Add Sn(II) DROPWISE until the yellow color just disappears. Then add ONE DROP of EXCESS Sn(II). 3. removal of the excess reducing agent Remove excess Sn(II) by adding HgCl 2 SnCl 4 2 + 2HgCl 4 2 SnCl 6 2 + Hg 2 Cl 2 (s) + 4Cl Mercurous chloride (white preciptate)
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If you have TOO MUCH Sn(II) (i.e. you screwed up Step 2) you will get the reaction SnCl 4 2 + HgCl 4 2 SnCl 6 2 + Hg( ) + 4Cl colloidal, grey-black preciptate DISCARD SAMPLE 4. Addition of special reagents to aid in detection of the endpoint and to
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This note was uploaded on 01/17/2012 for the course S 117 taught by Professor Stephenjacobson during the Fall '11 term at Indiana.

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S117LabLectureRedoxdeterminationofIron_001 - Redox...

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