A 0.500g sample is analyzed spectrophotometrically for manganese by dissolving it in acid and transferring to a 250 mL flask and diluting to volume. Three aliquots ae analyzed by transferring 50 mL portions with a pipet to 500 mL Erlenmeyer flask and reacting with an oxidizing agent, potassium peroxydisulfate, to convert the manganese to permanganate. After reaction, these are quantitatively transferred to 250 mL volumetric flasks, diluted to volume and measured spectrophotometrically.
By comparison with standards, the average concentration of the final solution is determined to be 1.25 x 10^-5M. What is the percent manganese in the sample?