Oxalate Complexes of Iron

Oxalate Complexes of smoothing weightliftIn coordination chemistry there are different types of ligands. Monodentate ligands donate whole one lone pair to the alloy ion. Bidentate ligands donate dickens pairs of electrons much(prenominal) as the oxalate ligands which can bind at two sites with the admixture ion, thus a coordination number of three ligands around one metal ion. Oxalate has four oxygens with each having a lone pair but it single uses two lone pairs to form a coordination compound.There are likewise multidentate ligands such as the EDTA which donate more than two pairs of electrons. Oxalate is can be regarded as a chelating agent. This means that two or more bonds are organism broken so that the ligand would be separated from the metal. These chelating ligands provide more stability to the confused than those with monodentate ligands.1The special K trioxalatoferrate (III) trihydrate and the bid (II) oxalate acquire a stereochemistry of an octahedral. Th e oxalate ion is a promiscuous field ligand according to the spectrochemical series. The Fe2+ has 6 electron in its d orbitals patch Fe3+ would have 5 electrons. The unpaired electrons of the iron (III) would have a uplifted spin and so behave paramagnetically.Fe2+ and Fe3+ electrons can both distribute themselves either in a low spin or a postgraduate spin arrangement.An example of the arrangement which is more favoured according to Hunds rule3d 4s 4p3d 4s 4pIron can accept 6 pairs of electrons because the orbitals are hybridised in a way to produce 6 orbitals of equal energy.A oxidation-reduction titration is a type of reaction which is based on redox equations amid the analyte and the titrant. Reduction-oxidation reactions are reactions where one of the component is being oxidize such as iron (II) to iron (III) thus becoming more positively charged while the other is being reduced thus it is gaining electrons and will puzzle less positive in its nature.Potassium permanga nate has the verbalism of MnO4- which can be reduced to Mn2+ in reducing conditions. This is an oxidizing agent.In this experiment the iron (II) oxalate and yard trioxalatoferrate(III) trihydrate were analysed. Then these two salts were analyzed for their iron and oxalate content and also the trial-and-error order of each salt was determined.Apparatus Pasteur pipette, weighing boat, spatula, watch glass, beat cyclinder stirring rod, Buchner funnel ,stopper, heating mantle, balance, beakers, thermometer, filter paper, ice-salt bath, flasks.ChemicalsChemicalBrand identifyFerrous ammonium sulfateGPRAldrichOxalic mordant dihydrateGPRN/A2M sulfuric acidGPRBDHAcetoneGPRBDHIron(II) oxalateGPRN/APotassium oxalate monohydrateGPRBDHHydrogen bleachGPRBDHEthanolGPRBDHPotassium permanganateGPRBDHZincGPRCarlo ErbaMethod try come on A readiness of Iron(II) Oxalate15g of ferric ammonium sulphate were dissolved in 50cm3 of warm pee which has been acidified with 2M sulphuric acid (1cm3).7 5cm3 of 10% oxalic acid resolving power was added with rapid stirring. The smorgasbord was heated gently to the simmering point and thus the yellowish decrease of ferrous oxalate was allowed to settle.The precipitate was removed by filtration on a Buchner funnel.It was serve thoroughly with hot pissing and then with acetone.The reaping was allowed to dry on the funnel under suction and weighed.The product was utilize for the next section. investigate B Preparation of chiliad trioxalatoferrate(III)Trihydrate3.25g of ferrous oxalate was susp terminateed in a warm final result of one thousand oxalate (5g in 15cm3 piddle.15cm3 of 20vol hydrogen peroxide was added from a burette whilst the solution was stirred continuously and maintained at 40OC. The solution contained the precipitate of ferric hydroxide.This was removed by heating the solution to boiling.10cm3 of 10% oxalic acid and then a further small amount of oxalic acid was added dropwise until the precipitate just diss olved.During the addition of oxalic acid, the solution was maintained proficient the boiling point.The hot solution was filtered.15cm3 of fermentation alcohol was added to the filtrate, any crystals that were organize by assuage heating were re-dissolved and put in a dark water system closet to crystallise.The crystals were collect by filtration on a Buchner funnel.These were washed with an equivolume mixture of ethanol and water and netly with acetone.This was dried,weighed and the product unploughed in the dark.Experiment C The analysis of the products for iron and oxalateIron(II) oxalate0.3g of oxalate was dissolved in 25cm3 of 2M sulphuric acid. The solution was heated to 60OC and titrated with 0.02M criterion potassium permanganate solution until the first permanent pink colour was discover.2g of coat scatter were added to the solution and boiled for 25 minutes.It was filtered through the glass beleaguer and the residual was washed with 2M sulphuric acid.The washin gs were added to the filtrate and this was titrated with a solution of threadbare potassium permanganateThe percentages of iron, oxalate, water of crystallization in the product and the data-based formula were determined.Potassium trioxalateoferrate(III) trihydrate0.2g of the complex were dissolved in 25cm3 2M sulphuric acid. This was titrated with 0.02M trite potassium permanganate solution until the first permanent pink colour was observed.2g of surface dust were added to the solution and boiled for 25 minutes.This was filtered through a glass wool and the residual was washed with 2M sulphuric acid.The washings were added to the filtrate and this was titrated with a solution of standard potassium permanganate.The percentage of iron and oxalate in the complex was determined.These were compared to the divinatory values.ResultsExperiment AFerrous oxalate 7.478gExperiment BPotassium oxalate5.058gPotassium trioxalatoferrate(III) hydrate6.019gFerrous oxalate3.273gExperiment CIron oxalate 0.301gVolume of potassium permanganate signFinalTitre valueVolume of potassium permanganate aft(prenominal) adding atomic number 30InitialFinalTitre valuePotassium trioxalatoferrate(III) trihydrate0.200gVolume of potassium permanganateInitialFinalTitre valueVolume of potassium permanganate after adding zincInitialFinalTitre valueCalculationIron(II) oxalateIron(II) and oxalate is oxidize by permanganate to Iron(III) and carbon dioxideIron(III) is reduced by zinc to Iron(II)MnO4- + 5Fe3+-+ 8H +Mn2 + + 5Fe2+ + 4H2OIron0.02 moles=1000cm3? 17.2cm33.4410-4 moles5Fe2+1MnO4-1.72X10-33.44X10-4moles1mole=56g1.7210-3moles=? 0.096gOxalate2MnO4- +5C2O42-+16H+ 2Mn2+ + 10CO2+8H2O52.4cm3-17.2cm3=35.2cm30.02moles=1000cm3? 35.2cm37.0410-4moles2MnO-45C2O42-7.04X10-41.76X10-31mole=88g1.7610-3moles=? 0.155g data-based formula0.096g+0.155g=0.251g0.301g-0.251g=0.05g1mole=18g? = 0.05g2.7810-3moles1.7210-3 moles 1.7610-3moles 2.7810-3moles1.7210-3 moles 1.7210-3moles 1.7210-3moles1 1.021 1 .6 2 FeC2O4.2H2O% of iron, oxalate and water of crystallisation in Iron(II) oxalateTheoreticalFe C2O4 2H2O56g 88g 36g180g 180g 1831% 49% 20%ExperimentedFe C2O4 2H2O0.096g 0.155g 0.05g0.301g 0.301g 0.301g31.89% 51.5% 16.6%Potassium trioxalatoferrate(III) trihydrateOxalate is oxidise by permanganate to carbon dioxideIron(III) is reduced by zinc to Iron(II)IronMnO4- + 5Fe3+-+ 8H +Mn2 + + 5Fe2+ + 4H2O0.02moles=1000cm3? 4.1cm38.210-5 moles5Fe2+1MnO4-4.110-4moles 8.210-5 moles1 mole=56g4.110-4moles =0.023gOxalate2MnO4- +5C2O42-+16H+ 2Mn2+ + 10CO2+8H2O0.02 moles=1000cm3? 26.4cm35.2810-4moles2MnO4-5C2O45.2810-41.3210-3 moles1 mole=88g1.3210-3 moles=? 0.116gK3Fe(C2O4)3.3H2O= RMM 471% of iron and oxalate in potassium trioxalatoferrate(III) trihydrateTheoreticalK3 Fe (C2O4)3 3H2O120 56 264 36471 471 471 47125.48% 11.9% 56% 7.64%ExperimentedFe (C2O4)30.023 0.1160.2 0.211.5% of iron in potassium trioxalatoferrate(III) trihydrate 58% of oxalate in potassium trioxalatoferrate(III) trihydratePrecaution sThe crystals were scraped from the filter paper which could lead to inaccurate filtration.The temperature of the solution was kept above 60oC during the titration of iron oxalate against potassium permanaganate.Titration apparatus was washed accordingly pipet and burette were washed first with water and then with the solution. Flasks were washed with water only.It was made sure that the burette was non leaky since it would affect the final result.The product of potassium trioxalatoferate(III) trihydrate was put in a dark cupboard since it is photosensitive causing loss of product.A heating mantle was used instead of a bunsen burner because ethanol is flammable.When the ethanol was added to the filtrate in incision B the solution was left to cool down since if the ethanol was added to the hot filtrate the ethanol could have evaporated.Sources of errorGlassware that was not calibrated properly could be a source of errorThe crystals were not dried completely and so would lead to hig her weight.Loss of the product due to transferring from the balance to the flask, due to air currents and unsteady movements.The color of the end point could be misleading as different people have different sensitivity to colors.Hydrogen peroxide could decompose in motiveless and so the oxidation of iron (II) and iron (III) would not be completed.Permanganate solution when allowed to stand in burette can undergo revealial vector decomposition to MnO2.Difficult in seeing the measurements on the burette because of the dark chromatic produced by the permanganate solutionFerric ion is reddish brown which could have interfered with the placard of the faint pink titration endpoint.DiscussionPreparation of iron(II) oxalateWhen oxalic acid is added to the mixture of ferrous ammonium sulphate in water and acidified with 2M of sulphuric acid, ions would form in solution.NH42FeSO42.6H2O + H2O 2NH4+ + 2SO42- + Fe2+ 2When adding oxalic acid to the solution oxalate ion forms which then reac ts with the iron(II) forming the iron(II) oxalic acid which is the product. This is the yellow precipitate which is removed by venturesomeness on a Buchner funnel. It is then washed with water and acetone to remove impurities.H2C2O4.2H2O + H2O 2H+ + C2O42- 2Fe2++ C2O42- FeC2O4. 2H2O 2Preparation of Potassium Trioxalatoferrate(III) TrihydrateWhen potassium oxalate is added to the ferrous oxalate an orange negociate complex would be formed. During the preparation of Potassium trioxalatoferrate (III) trihydrate the iron(II) in the iron(II) oxalate have to be oxidized to Iron(III). This is done by an oxidizing agent which in this case hydrogen peroxide is used. A brown precipitate of Iron(III) hydroxide would form2Fe2+ + H2O2 + 2H+ 2Fe3+ + 2H2O 3Fe3+ + 3OH- Fe(OH)3 3This could be removed by excess heating. 10% oxalic acid was added and so the oxalate ion could coordinate around the iron(III) metal forming a complex of Fe(C2O4). A ballpark solution would form in this stage. The fo llowing net equation would scram swan converting the iron(III) oxalate to trioxalatoferrate(III) ion.Fe2(C2O4)3 + 3 H2C2O4 + 6 H2O 2 Fe(C2O4)33- + 6 H3O+ 3The trioxalatoferrate(III) salt is soluble in water and would not precipitate out from an aqueous solution. Ethanol which is a less polar than water is added so that the salt would precipitate out since it is less soluble in ethanol. The precipitation is added by leaving the mixture overnight so that the salt would precipitate. This is placed in the dark because light would reduce the Iron(III) to Iron(II)3 K+ + Fe(C2O4)33- K3Fe(C2O4)3 3Made by Chem.WindowsAnalysis of the products for iron and oxalateIn the last part of the experiment the percentage of iron, oxalate and water of crystallisation was found by titration of the iron(II) oxalate with potassium permanganate which is the titrant. The volume of potassium permanganate needed to react with the known volume of analyte was found. The titration was tag when a faint pink colour appeared. This is the Mn2+ which serves as its own indicator to show when the titration is ready. In the first part the oxalate and iron(II) are both oxidized to Iron(III) and carbon dioxide. Zinc is added which acts as a reducing agent which reduces the iron(III) arse to iron(II).When titrating the potassium permanganate with the potassium trioxalatoferrate(III) trihydrate salt, a faint pink colour is observed when the stoichiometric point has been reached thus titration would be completed. In the first part the oxalate only is oxidized to carbon dioxide since iron(III) is already in its oxidized form. When zinc dust is added to the Iron (III) it is reduced to its reduced form iron(II).The solution would proceed colourless until all the oxalate salt is used. The solution is heated to 60OC since if the reaction takes place at room temperature it would be too slow.The oxidation of the oxalate anion which is an organic chelating agent, does not take place real easily. In th e presence of a metal ion, the rate of reaction increases since the oxidation would be kinetically more favourable when forming an intermediate metal chelate. 4 In this experiment this type of intermediate had formed during the conversion of the oxalate ion to carbon dioxide by the permanganate ion. 4 The permanganate ion is reduced to a commence oxidation state by taking an electron from the oxalate and so the carbon carbon bond in the oxalate is broken forming carbon dioxide.4Made by ChemWindows 4From the results one could observe that the percentages of iron and oxalate in the hypothetical effect which are 31% and 49% respectively are quite comparable to(predicate) to those percentages of the theoretical which are 31.89% and 51.5%. The theoretical percentage where brought by comparing the iron and oxalate to the RMM of the iron (II) oxalate. The theoretical % of water of crystallisation in this compound is 20% which resulted to be in close proximity to the experimented value that of 16.6%. When working the empirical formula of the oxalate iron an approximation was taken and so it was not very accurate. The ratio of 1.02 was rounded to 1 and the ratio of 1.6 was rounded to 2 for the water of crystallisation in the salt to result in the empirical formula of FeC2O4.2H2OWhen working the percentages of iron and oxalate in the potassium trioxalatoferrate(III) trihydrate the percentages were also very near to the theoretical value since the % of iron in the salt is 11.9% when working the theoretical and the experimented values were worked to be 11.5%. On the other hand, theoretically 56% of the trioxalatoferrate(III) trihydrate is oxalate and 58% oxalate in experimented value.ConclusionOne can conclude that the aims were reached. The preparation of these two compounds was done so that in the end the percentage of both iron oxalate in the iron(II) oxalate and the potassium trioxalatoferrate(III) trihydrate would be determined. The theoretical percentage of iron and oxalate of the theoretical were approximately very near those that were determined experimentally. The empirical formula of the iron(II)oxalate was also found to be FeC2O4.2H2O