Reduction-Oxidation Titration Essay

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Purpose: The following lab was conducted in order to determine the iron (〖Fe〗^(2+)) content in an unknown sample by way of reduction-oxidation titration using a standardized potassium permanganate solution. Theory: Titration is one of the most commonly used methods for determining the amount or concentration of an unknown substance. Chemical analysis can be performed on redox titrations, if the following conditions are met: “The reaction is thermodynamically spontaneous enough to be stoichiometric”, “The reaction is kinetically fast enough to give operationally ‘instant’ results”, “No side reactions occur”, and “a satisfactory indicator exists”. These conditions are what makes potassium permanganate (〖KMnO〗_4) a very useful analytical oxidation agent as it easily fits the criteria. The half reactions for this system are: Oxidation of 〖Fe〗^(2+): 〖Fe〗^(2+)→ 〖Fe〗^(3+)+1e^- Reduction of 〖MnO〗_4^-: 〖MnO〗_4^-+8H_3 O^++5e^-→ 〖Mn〗^(2+)+12H_2 O Which produces the following overall equation: 〖MnO〗_4^-+8H_3 O^++5〖Fe〗^(2+)→5〖Fe〗^(3+)+〖Mn〗^(2+)+12H_2 O Equilibrium is initially obtained at a very slow rate, therefore the titration is carried out in the presence of excess sulphuric acid (H_2 〖SO〗_4) at a high temperature; in order to drastically increase the rate at which equilibrium is attained. Potassium permanganate acts as its own satisfactory indicator since the reagent 〖MnO〗_4^- anion appears to be an intense purple colour while the product 〖Mn〗^(2+) cation has a colourless appearance. However, the end point must be read quickly as the permanganate end point gradually fades due to the 〖MnO〗_4^- reacting with the 〖Mn〗^(2+) that was formed during the titration. When performing the titration, one must be cautious as side reactions can occur and these side reactions must be prevented using appropriate chemical measures. If an insufficient amount of acid was
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