"A 0.1852-g sample of steel wasdissolved in dilute nitric acid, treated with ammoniumperoxidisulfate, transferred to a 50-mL volumetric flask, anddiluted to the mark with distilled water. Two 10.00 mL aliquots ofthe resulting unknown solution were placed in separate beakers towhich were added 5 mL of concentrated phosphoric acid and 0.40grams of potassium periodate. After the manganese was oxidized topermanganate, 5.00 mL of a standard potassium permanganate solutioncontaining 20.0 ppm Mn, was added to one of the beakers. Theresulting solutions were transferred to 50.0-mL volumetric flasksand diluted to the mark with distilled water. The absorbance of thesolutions were determined to be 0.118 and 0.327 at 525 nm.Calculate the %Mn in the steel."
This question is from an old exam,and included with this question was the answer key. The instructorcalculated the concentration of the solution to be 1.13 ppm, whileI calculated it to be x = 2.82 ppm. Did I do something wrong, ordid the instructor make a mistake? I'd hate to miss a similarquestion on my next exam simply because I missedsomething...thanks!
"A 0.1852-g sample of steel wasdissolved in dilute nitric acid, treated with ammoniumperoxidisulfate, transferred to a 50-mL volumetric flask, anddiluted to the mark with distilled water. Two 10.00 mL aliquots ofthe resulting unknown solution were placed in separate beakers towhich were added 5 mL of concentrated phosphoric acid and 0.40grams of potassium periodate. After the manganese was oxidized topermanganate, 5.00 mL of a standard potassium permanganate solutioncontaining 20.0 ppm Mn, was added to one of the beakers. Theresulting solutions were transferred to 50.0-mL volumetric flasksand diluted to the mark with distilled water. The absorbance of thesolutions were determined to be 0.118 and 0.327 at 525 nm.Calculate the %Mn in the steel."
This question is from an old exam,and included with this question was the answer key. The instructorcalculated the concentration of the solution to be 1.13 ppm, whileI calculated it to be x = 2.82 ppm. Did I do something wrong, ordid the instructor make a mistake? I'd hate to miss a similarquestion on my next exam simply because I missedsomething...thanks!
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