Paper Experiment 4

Paper Experiment 4 - Abstract In this lab, one uses the...

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Abstract In this lab, one uses the techniques of redox titrations and spectrophotometry and their use in determining the empirical formula of a potassium salt complex of certain unknown. An iron oxalate will be synthesized via redox reactions, then isolated and purified so it may be analyzed for its composition of iron and oxalate. The determined empirical formula of the complex was found to be K[Fe 3+ (C 2 O 4 )] · 2H 2 O. This value is somewhat close to the accepted value of K 3 [FeIII(C 2 O 4 )3] · 3H 2 O. The average number of millimoles of iron was found to be 137.22 ± 35.8. The average number of millimoles of oxalate was found to be 796.5 ± 8.38. The ratio of millimoles of oxalate to millimoles of iron was 1:6. The methods used proved to be inaccurate. Introduction After synthesizing, isolate and purified, K w [Fe x (C2O4) y ] z H2O from experiment 4A, one should observe the value of w, x, y, and z value through experiment 4B, and 4C. In the experiment 4B, volumetric analysis is used to determine the weight percentage of oxalate ligands in the iron (III) oxalate complex synthesized in the part one. Volumetric analysis uses volumetric measurements to measure the specific amount of a substance present in an unknown sample. The concentration of a standard solution can be determined by standardizing it, which involves titrating it against and exactly determining the mass of the primary standard. In this experiment, the primary standard is Na 2 C 2 O 4. And, it determines the standardized concentration of permanganate ion which is already prepared and stored in the dark after standardization. For this experiment, a redox titration is used with the permanganate ion, MnO 4 - . In this titration, a second indicator which is a compound that does not react with the two reactants in the titration but changes color near the stoichiometric point is unnecessary because one of the species used in this titration changes color by itself as it reacts. The indicator for this experiment is the titrant, the permanganate which is a strong oxidizing agent with purple color capable of converting oxalic acid to carbon dioxide and water. As it reacts, it turns into manganate ion which is clear (faint pink). The reaction goes: MnO 4 - + 5C 2 O 4 2- + 16H + → 2Mn 2+ + 10CO 2 + 8H 2 O An oxidizing agent goes through reduction, which means it accepts electrons. The reducing agent which donates electrons is the oxalic acid. This reaction will occur best in a strong acid solution as the oxalate ions will be fully protonated to oxalic acid (H 2 C 2 O 4 ). The analyte for this experiment is the unknown Fe-Oxalate complex to determine C 2 O 4 2- . This part of the experiment involves finding the stoichiometric point, in which the moles of the titrant equals to the moles of the analyte. In this experiment, the end point which is when the reaction changes color due to the fact that a certain pH is reached is the same as the stoichiometric point as no second indicator is used. The manganate ion is also used as
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Paper Experiment 4 - Abstract In this lab, one uses the...

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