How can I convert molar concentration to mass percent? I am trying to find the %

Question

How can I convert molar concentration to mass percent? I am trying to find the % Mn in an unknown sample of steel. I plotted mass of Mn in standard steel against absorbance as I was instructed. From this, I found molar concentration using Beer's law. I tried using the molar mass of Mn and the volume of the solution with the molar concentration to find the mass, but the answer I got doesn't make sense. (It's a mass of manganese even greater than the mass of steel I started with, so that's impossible). Please help.

I forgot to add: I wasn't given the chemical formula of the steel. It's not given anywhere in the lab manual, or in the chemical equations.

Explanation / Answer

This is a sample problem i have ...

let the Mn concentration in the measured sample from steel is equal to:
1.7603 ppm (mg L-1)
Now we need to know how much Mn was in the total steel sample.

Recall that the steel was digested then diluted to 250 mL. We then took 20 mL of this solution
and diluted to 50 mL for the absorbance measurement.

1.7656 mg L-1 Mn x (0.050 L / 0.02 L) x 0.250 L = 1.1035 mg of Mn total

Finally we can calculate the mass percent of Mn in our steel sample
(1.1035 x 10-3 g Mn) / (1.0032 g steel) x 100 = 0.11 %

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