Question

You weighed out 0.3267 g of steel and completely dissolved it in 6 M nitric acid upon heating in the fume hood for an hour. The entire contents were transferred to a 250 mL volumetric flask, which was diluted to the mark with DI water. 10 mL aliquots were transferred to six different 250 mL Erlenmeyer flasks. To each Erlenmeyer flask, 5 mL of 85 % H3PO4 were added along with 0.4 g of KIO4. Increasing volumes, Vs of 0, 1, 2, 3, 4, or 5 mL, of 0.015 M Mn standard solution were also added to each Erlenmeyer flask. The solutions were boiled gently for 5 minutes, which resulted in a pink color change. The entire contents of each Erlenmeyer flask were transferred to six different 50 mL volumetric flasks, and diluted to the mark. Absorbance values from each flask were measured. Absorbance was plotted versus the volume (in mL) of standard manganese solution, Vs,f that was added to each of the six solutions. The resulted linear calibration equation resulted from this analysis. y = 0.3243x + 0.1512 Given that the molar mass of manganese is 54.94 g/mol, calculate the mass percent of the manganese in the original steel sample. Report your answer with three significant figures.

Answer 1