Archeologists in China found an ancient paint pigment they knew contained only two oxide compounds, iron (III) oxide and nickel (II) oxide, it took 20.00 mL
of 0.125 M sulfuric acid to react with the iron compound and another 16.41 mL of
the acid to react with the nickel compound. What was the original mass of the
sample? *

The content of manganese (mn) in steel was determined spectrophotometrically and with the use of the standard addition method. an unknown sample of mn from a digested steel sample gave an absorbance of 0.185 when analyzed spectrophotometrically. when 5.00 ml of solution containing 95.5 ppm mn was added to 50.0 ml of the unknown steel solution (digested sample), the absorbance was 0.248. calculate the concentration, in parts-per-million (ppm), of mn in the digested steel sample solution.