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Determining the iron content in a sample of steel wool.

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Determining the iron content in a sample of steel wool Natalie Loo 12A Aim: To find the percentage of iron in a sample of steel wool. Method: 1. Weigh accurately about 1g of steel wool and add enough dilute sulphuric acid to cover it in a conical flask. Heat the flask gently until the reaction starts. 2. When all the steel wool has dissolved, filter the solution and the washings from the flask into a beaker. 3. Make the solution up to 250ml in a volumetric flask with boiled, cooled distilled water, washing the beaker out with boiled distilled water twice. 4. Calculate the mass of KmnO4 needed to make up 500ml of 0.02M solution. 5. Weigh out approximately this mass of solid KmnO4 and dissolve in 500ml of water in a 1L beaker. 6. Cover the beaker with a watch glass and boil it for 10 minutes. 7. Cool the solution and filter it through glass wool into a clean storage bottle. ...read more.


17. Repeat the titration in the usual way. Diagram: Results Table: Mass of steel wool 0.96g Mass of KMnO4 1.64g Volume of KMnO4 511ml Mass of oxalic acid 1.58g Volume of oxalic acid 250ml Pipette Solution 20cm3 Oxalic acid Burette Solution 50cm3 Potassium permanganate Trail 1 2 3 4 Burette Reading Final 18.6 38.5 18.8 37.6 18.8 Initial 0 18.6 0 18.8 0 Volume used (titre)/cm3 18.6 19.9 18.8 18.8 18.8 Mean (titre)/cm3 18.8 Pipette Solution 20cm3 Iron (II) Sulphate Burette Solution 50cm3 KMnO4 (standardized) Trail 1 2 3 4 Burette Reading Final 14.6 26.6 12.1 25.2 37.2 Initial 0 14.6 0 13.1 25.2 Volume used (titre)/cm3 14.6 12.0 12.1 12.1 12.0 Mean (titre)/cm3 12 .05 Conclusion: Fe Fe2+ 0.96g Fe2+ Fe3+ Conc. = moles/vol. Vol. of oxalic acid = 20cm3 (per titration) Conc. Of oxalic acid = (1.58/126.07)/(25/1000) = 0.050130879 mol dm-3 Moles of oxalic acid = (20/1000) x 0.050130879 = 1.002617593 x 10-3 moles of oxalic acid 2MnO4- + 6H+ + 5HCOOCCOOH --> 2Mn2+ + 8H2O + 10CO2 2MnO4- = 5HCOOCCOOH 2/5 MnO4- = HCOOCCOOH Moles of MnO4 = 1.002617593 x 10-3 x 2/5 = 4.010470374 x 10-4 Conc. ...read more.


I might have also made some random errors, looking at the results, there's a difference between the highest and the lowest titre. In the titration of standardizing the potassium permanganate, the difference is 1.3cm3. In the titration of iron (II) sulphate and the standardized potassium permanganate, the difference is 2.6cm3. The differences are random errors in the procedure. I might not be watching the end point and I might not be measuring out solutions accurately. Also, it is quite difficult to observe the colour change as the colour changes in a split second. To increase the reliability and the accuracy of the experiment, procedures of the experiment should be improved in some way. More readings should be taken in the titration to increase the reliability. Also, the whole experiment could be repeated for 3 times to increase the reliability. Taking more results and repeating procedures could increase the reliability of the experiment. It's also of advantage to take the results of a wider range. Taking each individual reading with caution could increase the accuracy of the experiment. ...read more.

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