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# Titration To Determine the Concentration of an Iodine Solution.

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Introduction

TITRATION TO DETERMINE THE CONCENTRATION OF AN IODINE SOLUTION. Introduction The volume of iodine solution needed to neutralize the sodium thiosulphate. You simply titrate the sodium thiosulphate against the solution of iodine using starch solution as an indicator. Then when you have calculated the concentration of the sodium thiosulphate can use it in turn as a standard solution, to find the concentration of the other substance. A redox reaction has accured. I2 + 2e- --> 2I- S2O32- + I2 --> S4O62- + 2e- 2 S2O32- + I2 --> 2I- + S4O62 Safety The iodine is strongly oxidising. At all times through the experiment you must wear eye protection and lab coats. When filling the pipette be careful it does not break. And when filling the burette make sure it is below eye level. If any spillages have been made clean them up and report it. ...read more.

Middle

Stop adding acid when a single drop turns the solution deep red to yellow. One drop accuracy. Record the new level of sodium thiosulphate in the burette. Calculate the volume of acid used. Carry out four titrations, one trial and three accurate. Give your answer to 2 decimal places. Results Titrations Initial reading Final reading volume used cm3 1 0.00 29.60 29.60 2 0.00 29.65 29.65 3 0.00 29.60 29.60 4 0.00 29.70 29.70 Calculations Average volume of potassium manganate v11 used, from three accurate titrations: 29.65 + 29.60 + 29.70 = 29.65 cm3 Weighing board = 0.97 Altogether = 7.09 Na2S2O3.5H20 I2 + 2e- --> 2I- reduction S2O32- + I2 --> S4O62- + 2e- oxidation 2 S2O32- + I2 --> 2I- + S4O62 Mass 6.12 Moles * mr 0.024 * 248 Moles 0.024 Molarity * vol/dm3 ? * 250/1000 = 0.096 =0.01 29.65 0.1 mol.dm3 S2O3 = 25.00 cm3 I2 2 S2O32- + I2 --> 2I- + S4O62 ...read more.

Conclusion

We could have lost some of the solution when we were transferring it from the pipette to the conical flask. It could have remained on the side of the pipette and the conical flask. We could not collect all the solutions no matter how hard we tried. Due to equipment error. Instrument accuracy/ lowest reading * 100 = ans 0.05/ 28.40 * 100 = 0.17% For the burette. This shows that the equipment are not absolute accurate. Another factor could have been the air around us. Or standing near the window and the outside temperature could have its effect. Other instruments could be used which have a better accuracy point. More sophisticated measuring equipment could also be another point to notice. Conclusion The morality of the iodine solution was 0.0593 moldm3. The results were close together and the indicator changed quickly at the end point. If you were to repeat this experiment you could make it better by using a different indicator instead of starch, or using a different concentration of sodium thiosulphate. 28/04/2007 AKRAM ALI ...read more.

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