Quality control samples were taken of a batch of nickel-iron alloy produced by I

Question

Quality control samples were taken of a batch of nickel-iron alloy produced by Ironic Steel, Inc. in the furnace at their Springfield plant. The alloy must contain 43% nickel, plusminus 0.5%, with the remaining percent iron. A 1.200 g sample was dissolved in hydrochloric acid and diluted to 100 mL in a volumetric flask. The Beer's law plot for the absorbance of Fe(NO_3)_3(aq) versus its concentration is listed below. Calculate the percent iron contained in the alloy sample. Based on your results, is the batch of 42% nickel-iron alloy acceptable?

Explanation / Answer

From the given experiment

Absorbance of unknown sample solution = 0.3730

concentration of Fe in dilute solution = 0.3730 x 0.1/0.3530

                                                           = 0.10566 M

moles of Fe in solution = 0.10566 M x 0.1 L

                                     = 0.010566 mol

grams of Fe in sample = 0.0105666 mol x 55.845 g/mol

                                     = 0.5901 g

percent Fe in the sample = 0.5901 x 100/1.20

                                         = 49.175%

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