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# Devise a volumetric procedure to determine the percentage of Iron(II) and Iron(III) in a mixture containing both.

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Introduction

M. Usman Ali (71D) THE ESTIMATION OF IRON(II) AND IRON(III) IN A MIXTURE CONTAING BOTH Aim: To devise a volumetric procedure to determine the percentage of Iron(II) and Iron(III) in a mixture containing both. Background/Planning: Iron is a transition element, and all transition elements may be found in a variety of oxidation states, for example iron exists as both, Iron(II) and Iron(III). These kinds of elements can react with both oxidising and reducing agents due to the fact that they can be converted from one oxidation state to another. Working out the percentage composition of both of the Iron ions will require two separate titrations. One of the titrations will react with only one of the ions however the other will react with the mixture as a whole. To be able to carry out a titration in which of all the mixture will react, a preliminary reaction will need to be done. Potassium Manganate (KMnO4) is an oxidising agent and will react with Iron(II) but will not react with Iron(III). This can be therefore used to work out the percentage of Iron(II) in the solution. To work out the percentage composition of Iron(III) a separate reaction will need to be carried out first. The Iron(III) ...read more.

Middle

Record the initial volume of the Potassium Manganate in the burette, reading from the bottom of the meniscus and record to two decimal places. Carefully place the pipette into pipette filler and place it in the iron solution. Turn the thumb dial to suck up the solution. Suck up more solution then what is needed. Remove the pipette filler and cover the top of the pipette with your index finger and apply pressure. By decreasing the pressure the level of the solution will fall. Transfer the solution into a conical flask. Touch the end of the pipette against the inside of the conical flask to release the remaining solution. Add about 20 cm3 of dilute sulphric acid to the solution in the conical flask. Place the conical flask on the white tile underneath the jet of the burette and allow about 2 cm3 of the Potassium Manganate out into the conical flask and swirl the solution. As soon as the solution turns pink, close the tap and record the volume of Potassium Manganate used. Use this as the trial titration. Refill the burette as before recording the initial volume and wash out the conical flask using distilled water and fill as you did before. Repeat the titration before, however when within 2 cm3 of the volume recorded for the trial titration, slow the flow of the Potassium Manganate so it is coming out drop by drop. ...read more.

Conclusion

in solution = Moles x RMM of iron = C x 55.8 = D * Titration 2. {Iron(II) and Iron(III)} Moles of MnO4- used = (Volume x concentration)/1000 = (Volume x 0.02)/1000 = E Moles of iron(II) in 25 cm3 = A x 5 (using mole ratio) = F Moles of iron(II) in 200 cm3 = B x 8 = G Mass of iron(II) in solution = Moles x RMM = C x 55.8 = H Mass of iron(III) present = H - D = X * The Percentage Composition by mass for each iron : 1. Iron(II) = (D/H) x 100 2. Iron(III) = (X/H) x 100 Health and Safety: Potassium Manganate : Harmful by ingestion Danger to the environment Sulphuric Acid : Corrosive Ingestion will be fatal Potassium Thiocyanate : Harmful by ingestion Skin contact may lead to ulceration Zinc : Flammable May act as an irritant * Safety glasses & lab coats must be worn. * Care must be taken when heating the solutions as chemicals may spit. * Tongs should be used at all times when handling the zinc to avoid skin contact. * If any chemical comes into contact with skin, wash effective area immediately with warm water, seek medical advice if necessary. * Care should be taken when moving around glass. Breakage should be reported immediately. * All practical work should be carried out in a well-ventilated area. ...read more.

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