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Chemistry report - In this experiment, it is a redox titration method to standardize a solution of potassium manganate(VII) by an iron(II) salt (ammonium iron(II) sulphate).

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Introduction

´╗┐EXPERIMENT 3: Standardize a solution of potassium manganite(VII) by an iron(II) salt (ammonium iron(II) sulphate). Objective: 1. To standardize a solution of potassium manganate(VII) by an iron(II) salt (ammonium iron(II) sulphate). Introduction: In this experiment, it is a redox titration method to standardize a solution of potassium manganate(VII) by an iron(II) salt (ammonium iron(II) sulphate). So, the word of redox is related to the oxidation and reduction. Oxidation numbers describe the number of electrons the atom will gain or lose during a reaction. Each atom in an equation can be assigned an oxidation number according to certain rules. Oxidation occurs when the oxidation number of an atom increases while reduction occurs when the oxidation number decreases. Potassium manganate (VII) (KMnO4) solution is standardised by titration against the ammonium iron(II) sulphate, FeSO4 .(NH4)2SO4.6H2O. Potassium manganate is widely used as an oxidizing agent in volumetric analysis. While the ammonium iron(II) sulphate is used as a primary standard to standardize the KMnO4 solution. In this experiment, ammonium iron(II) sulphate crystals are the stable compound that remain as solid in room temperature. Hence, the ammonium(II) ...read more.

Middle

Calculate the number of moles of Fe2+ ions in 10.0 or 25.0 cm3 of the solution pipetted. No. of moles of Fe2+ = No. of moles of FeSO4 .(NH4)2SO4.6H2O 250.0 cm3 of FeSO4 .(NH4)2SO4.6H2O contain 0.025 mol of Fe2+ ions, Thus, no. of moles of Fe2+ in 25.0cm3 = 0.025250 x 25 = 0.0025 mol 3. Calculate the number of moles of MnO4- which reacted during titration. MnO4- + 8H+ + 5Fe2+ → Mn2+ + 5Fe3+ + 4H2O 1 mole of MnO4- = 5 moles of Fe2+ Hence, no. of moles of MnO4- = 0.00255 = 0.0005 mol 4. Calculate the concentration of the manganate(VII) ions, MnO4-, in mol dm-3 and in g dm-3. ( a ) in mol dm-3 Concentration of MnO4- = 0.0005 mol0.02663 dm-3 = 0.02 mol dm-3 ( b ) in g dm-3 Mass = no. of moles × molar mass = 0.0005 × 55+4(16) = 0.06 g Concentration of MnO4- = 0.06 0.02663 = 2.25 g dm-3 5. ...read more.

Conclusion

sulphate, the initial and final readings of the burette is recorded and repeated 3 times, includes 1 for rough reading and another 2 for accurate readings. So, the average value of potassium manganate(VII) is calculated to get a more accurate result. In the summary of this experiment, 25.00 cm3 of the acidified ammonium iron(II) sulphate required 26.63 cm3 of the potassium manganate(VII) solution for reaction. There are some precaution steps in this experiment in order to obtain the results more accurately and precisely. During the process of the experiment, the pipette is rinsed with a little sulphuric acid to remove water present inside the pipette. This is the way to prevent the water from diluting the acid that is poured inside the pipette. In the same way, burette is also rinsed with a little of potassium manganate(VII) solution. Besides, a piece of white tile that placed below the conical flask is used to enable us to detect the end point clearly, which the colourless solution changes to a light pink solution. Moreover, the eyes must be placed at the same level as the meniscus of the solution inside the burette in order to obtain an accurate of initial and final readings. ...read more.

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