Question

Both the oxalate ligands and the vanadium are oxidised by the KMnO4 with the oxalate decomposing and leaving the system as CO2(g). Therefore, the first titration step titrates both the oxalate and the vanadium. 0.3g of the complex salt was dissolved in 60ml of H2SO4 (2M). This solution was diluted to 100ml with distilled water. Take 25ml aliquot and heat the solution to 80 oc. Titrate this hot solution with potassium permanganate 0.01M until the bright pink colour is first seen. The vanadium must be reduced back down in order to perform a second KMnO4 titration this time with just the vanadium being oxidised as there is no oxalate left in the system. Add 0.1g of sodium sulphite to the oxidised solution. The volume of first titration is 22.1ml and 5.4ml for the second titration. A)Calculate the moles of oxalate from the difference between the first and second titrations. (show your working). B)Calculate the number of mole of vanadium from the second titration. C)Calculate the vanadium: oxalate ratio.

Answer 1

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