Overview
5. You perform a redox titration of 100 mL of a 0.100 M Fe2+ in 0.500 M H2SO4 solution with 100 mL of a 0.0200 M potassium permanganate solution. Write down the overall/balanced chemical reaction of this titration. How many electrons are involved in the redox reaction? Calculate the half potential for manganese in this titration.
6. Selenium (Se) is an important trace element of human nutrition and a crucial cofactor of the enzyme glutathione peroxidase, which plays a key role in the detoxification of xenobiotics in living cells. However, at high concentrations Se is toxic. Selenium in a 10.0 g soil sample is distilled as the tetrabromide, which is collected in aqueous solution where it is hydrolyzed to selenite (SeO32-). The SeO32- is determined iodometrically, requiring 4.5 mL of standard sodium thiosulfate for the titration. The thiosulfate concentration is 0.049 mg Na2S2O3/mL. What is the balanced chemical reaction of this titration? What is the concentration of selenium in the soil (in ppm)? Considering that soil selenium levels in excess of 5 ?g/g are considered to be toxic to animal life, evaluate your finding. amu(Se) = 78.96 g/mol.