A 25.00-mL sample of well water containing dissolved iron was treated with hydroxylamine hydrochloride, pH 5 buffer, and 1,10-phenanthroline, and diluted to 100.0 mL. Absorbances were measured at 510 nm using a 1.00-cm cell.
• The prepared sample had an absorbance of 0.346 (all absorbances measured relative to water as reference).
• A standard solution prepared in the same fashion, containing 5.00 mL of 5.00 x 10-4 M Fe(ClO4)3 and the reagents (no sample) had an absorbance of 0.284.
• The reagent blank had an absorbance of 0.003.
Calculate the molar concentration of iron in the original well water sampl