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Introduction

Background An acidified solution of manganate (VII) ions or permanganate is a strong oxidizing agent and is often used for analysis of solutions for ferric ions (Iron (III)), by reducing the ferric to ferrous, and then titrating with a permanganate solution of known concentration. The relevant half equations are: Potassium permanganate solutions have a short shelf life. Their decomposition is catalysed by light, heat, acids, bases Mn (II) and MnO2. Thus, potassium permanganate solutions need to be standardized immediately prior to use to determine their precise concentration. A primary standard is a substance that is available in pure form, is not hygroscopic and is easily dried, is stable in both pure form and in solution. Sodium oxalate (Na2C2O4) is a white crystalline solid and is readily available in pure and stable form. The titration is usually carried out at 70 �C so that the rate of reaction is sufficiently fast. The solution temperature should remain above 60 �C at the end point. Hydrogen peroxide is regarded as an "environmentally friendly" alternative to chlorine for water purification and wastewater treatment. Because hydrogen peroxide decomposes in the presence of heat, light, or other catalysts, the quality of a hydrogen peroxide solution must be checked regularly to maintain its effectiveness. Table 1. Equipments and uncertainties Equipment Uncertainties Weighing boat n/a Spatula n/a Electronic Balance �0.020g Volumetric Pipette 20ml �0.040ml Burette �0.10ml Stand n/a Funnel n/a Conical Flasks 100 cm3 and 250 cm3 n/a Sulfuric acid 4.0 mol dm-3 n/a Thermometer � 0.20�C Hot Plate n/a Distilled Water Wash Bottle n/a Measuring cylinder 250ml, 100ml and 10ml �2.0ml, �1.0ml and �0.20ml Results: Table 2. ...read more.

Middle

In this equation, sodium and potassium is not take part in the equation because they are spectators. Hence, using the balanced equation, it is possible to determine the concentration of the potassium permanganate ion. Again, from the half equation given above the background information; it is possible to write down a balance equation of hydrogen peroxide with the permanganate ion. Again, potassium in potassium permanganate does not take part in this equation because it is a spectator. With the balanced equation, it is able to calculate the number of grams of hydrogen peroxide in the unknown sample. Also using this, percentage of hydrogen peroxide could be determined by the mass assuming the density of the hydrogen peroxide solution to be 1.00g/ml. g Conclusion and Evaluation: In this titration experiment, potassium permanganate was used as an indicator for both of the titration involving sodium oxalate and hydrogen peroxide. In addition, sulfuric acid was used as a provider of hydrogen ion to the solution. In case where if there is an insufficient amount of acid is added in either titration, with sodium oxalate or with hydrogen peroxide, some of the permanganate ions will be reduced to MnO2 instead of Mn2+. If the half equations are rewritten by replacing Mn2+ by MnO2; Comparing with the previous half equations with Mn2+; It can be seen that in the 1st titration, the molar ratio between MnO4- with C2O42- in the titration with Mn2+ is 2:5, whereas the molar ratio between MnO4- with C2O42- in the titration with MnO2 is 1:2. ...read more.

Conclusion

Making one person in the group to carry out the titration to reduce the subjectiveness of end point Exact titration amount of potassium permanganate While in the process of titrating, the amount being poured into the solution from the burette, cannot be controlled fully by human hand Repeat the process several times and create an average of the all data gained from the titration Lack of trials of titration done during the given time The processes of titrations were to be carried out very slowly to gain the exact data. As there was limited time, there were only few titration experiments could be done. By increasing the number of trials for both of the titration experiments, then it will reduce the uncertainties, hence may have 0% difference between theoretical value of concentration of hydrogen peroxide and gained value of concentration of hydrogen peroxide. Heat control for the oxalate solution Oxalate solution had to be more than 60�C but not boiling (around 60�C~80�C) If the temperature of the solution went lower than 60�C, then the reactions are not completely done Turning the air conditioner off to stop the temperature drop due to the wind created by the air conditioner Windows shut Potassium permanganate decomposes in air Some of potassium permanganate decompose in air over time, therefore extra potassium permanganate are used up than needed Seal the top of the burette with a cork to block the potassium permanganate decomposing in air ...read more.

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