Answer: A 0.450-g sample of steel contains manganese as an

Chapter 21, Problem 57P

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A 0.450-g sample of steel contains manganese as an impurity. The sample is dissolved in acidic solution and the manganese is oxidized to the permanganate ion \(\mathrm{MnO}_4^{\ \ -}\). The \(\mathrm{MnO}_4^{\ \ -}\) ion is reduced to \(\mathrm{Mn}^{2+}\) by reacting with 50.0 mL of 0.0800 M \(\mathrm{FeSO}_{4}\) solution. The excess \(\mathrm{Fe}^{2+}\) ions are then oxidized to \(\mathrm{Fe}^{3+}\) by 22.4 mL of 0.0100 M \(\mathrm{K}_{2} \mathrm{Cr}_{2} \mathrm{O}_{7}\). Calculate the percent by mass of manganese in the sample.