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The preparation, analysis, and reactions of an ethanedioate complex of iron

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Experiment 1 Title: The preparation, analysis, and reactions of an ethanedioate complex of iron Date: 5-2-2007 and 12-2-2007 Objective: * To prepare oxalate complex of iron from the reaction with ammonium iron (II) sulphate * To deduce the oxidation states of iron in the complex * To determine the amount of iron and oxalate in the oxalate complex of iron by titration. * To investigate the molecular formula of the complex formed by preparation, analysis and the reaction of an ethanedioate (oxalate) complex of iron * To deduce the chemical properties of the complex of iron from the reactions with dilute sodium hydroxide, ammonium thiocyanate solution, and ammonium thiocyanate solution in the presence of dilute sulphuric acid respectively, compared to the reaction of iron(III) chloride and the reagents above. Introduction Iron is nearly always determined by reduction to the dipositive state followed by titration with manganate(VII) or dichromate(VI). However oxalate would interfere and must be determined first by titration with permanganate. After titration, any iron present will be Fe(III) then reduced by tin(II) chloride and hydrochloric acid, and the Fe(II) determined with dichromate. Materials and Methods Procedure for prepartion 10.53g of ammonium iron(II) sulphate, (NH4)2Fe(SO4)2?6H2O , was weighed using a rough balance and put into a 400cm3 beaker, followed by the addition of few drops of dilute sulphuric acid and 30cm3 of water, and heated until a clear solution was obtained. Then a solution of 5.08g oxalic acid dihydrate in 30cm3 of water was added. ...read more.


0.38 0.38 Initial reading (cm3) 1st 0.8, 2nd 2.6 1st 5.7, 2nd 18.3 Final reading (cm3) 1st 48.9, 2nd 5.7 1st 48.2, 2nd 18.8 Volume of 0.02M permanganate used (cm3) 48.1+3.1=51.2 42.5+0.5=43 The average of the weight of complex = (0.38+0.38)/2 = 0.38g The average volume of permanganate used = (51.2+43)/2 = 47.1 cm3 Titration with dichromate Weight if complex (g) 0.38 0.38 Final reading (cm3) 23.2 35.5 Volume of 0.01M dichromate used (cm3) 11.2 12.3 The average of the weight of complex = (0.38+0.38)/2 = 0.38g The average volume of dichromate used = (11.2+12.3)/2 = 11.75cm3 Observation of the reactions of the complex oxalate Iron(III) chloride Complex Dilute sodium hydroxide solution The solution changed from yellow to pale yellow solution with reddish brown precipitate. The solution changed from pale green to pale yellow solution with reddish brown precipitate. Ammonium thiocyanate solution The solution changed from yellow to clear dark red solution. No observable change Ammonium thiocyanate solution + dilute sulphuric acid The solution changed form yellow to dark red solution. The solution change form pale green to red solution. Discussion Question 1)Deduction for the qualitative test In the qualitative test, both the complex and iron (III) chloride were reacted with dilute sodium hydroxide solution respectively and brown precipitates were formed that indicated the presence of Fe(OH)3(s) : Fe3+ + 3OH- � Fe(OH)3 For the reaction between iron (III) ...read more.


According to our calculation, the formula of the hydrated complex is K3[Fe(C2O4)3].6H2O. However, the formula of the hydrated complex should have 3 water molecules theoretically. This may due to the inaccurate mass of the complex due to the experimental error such as the presence of extra water or impurities which increases the final mass of the complex. Some important notes and safety precaution Aluminium foil should be used to wrap the conical flask containing the product before putting it in a dark place as the product is photosensitive. Sintered-glass was used instead of filter paper as filter paper is easier to retain the product causing lost in yield. After the suction filtration, remove the rubber tube first instead of the sintered-glass funnel to prevent sucking back of the filtrate. As concentrated hydrochloric acid was highly corrosive, it can attack the respiratory system and skins, the adding process should be preceded in the fume cupboard and should take more care when pouring it. Moreover, most of the reactants used in this experiment are highly toxic, we should avoid handling all these solid and avoid spillage of solutions. When handling highly flammable ethanol, no naked flames in the vicinity should exist. Conclusion: In this experiment, the mass of the complex prepared was 5.925g and the percentage yield is 41.04%. The oxidation state of the iron in the complex is +3 and the mass of complex containing 1 mole of iron is 539.01g. The formula of the hydrated complex is K3Fe(C2O4)3?6H2O and the complex is optically active according to its structure. ?? ?? ?? ?? 1 ...read more.

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