If 7.0 moles of HCl is added to enough iron that the HCl is completely used up, how many moles of hydrogen gas will be produced?

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.

Chemistry worksheet - i am not sure what they are asking for exactly?

What is the chemical formula for dihydrogen monoxide