Determine%OxalateinIronOxalatoSalt

Determine%OxalateinIronOxalatoSalt - The Determination of...

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The Determination of Percent Oxalate in an Iron Oxalato Salt Experiment #6 Olivia D. AP Chemistry Emmaus High School November 19, 2007
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Abstract In this experiment we are determining the percent oxalate in the complex iron crystals synthesized in the first experiment. The percents determined in this lab will be used to determine the empirical formula of the crystals, K x Fe(C 2 O 4 ) y • zH 2 O. Group 7 determined, on average, the percent oxalate to be 55.3% with a standard deviation of 1.48. The class determined the percent potassium to be 54.7% with a standard deviation of 1.41. Apparatus magnetic stirrer buret KMnO 4 Iron oxalate solution
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Theory In this lab, we are titrating a standardized solution of 0.0200 M KMnO 4 against a solution of green oxalate crystals and sulfuric acid in ordered to determine the empirical formula of the green crystals, K x Fe(C 2 O 4 ) y • zH 2 O. In this lab we are not using an indicator to determine the endpoint of the reaction. When permanganate is in solution, it creates a pinkish-purple color. So, the endpoint of the reaction is reached when the first permanent pink color appears. This means there is a slight excess of the permanganate. A permanent color in this lab may take a minute or two to determine. The reaction in this experiment physically takes place very slowly, which is why the solution is heated, so the pink which appears fades as the reaction occurs over time. Also, one must be familiar with oxidation reduction reactions. In this type of reaction, electrons are transferred from one molecule to another and the oxidation states of some ions are therefore changed. If electrons are lost in the reaction and therefore the oxidation state of the ion goes up, the process is called oxidation. In this reaction, the carbon is considered to be oxidized because it changes from a 3+ oxidation state to a 4+. If electrons are gained in the reaction and therefore the oxidation state of the ions goes down, the process is called reduction. In this lab, the manganese is considered to be reduced because its oxidation state changes from 7+ to 2+. Because the manganese causes the carbon to be oxidized, it is considered the oxidizing agent. By similar thought, the carbon is considered to be the reducing agent because it causes the manganese to be reduced. The net ionic equation for the reaction is: 2MnO 4 - + 5H 2 C 2 O 4 + 16H + 2Mn 2+ + 10CO 2 + 8H 2 O
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In the experiment, the green crystals are put into solution. Normally when in solution, iron causes a yellowish brown color. When the oxalate reacts with the potassium permanganate, the iron is put into solution and a yellowish color results. So, at the beginning of the titration 85% phosphoric acid is added to the green crystal solution. The phosphoric acid reacts with the iron to eliminate the yellow color and make it easier to detect the color change in the reaction. With the conclusion of this part of the lab, we have all the necessary information in order
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Determine%OxalateinIronOxalatoSalt - The Determination of...

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