Need help with these lab questions

Question

Colorimetric determination of Manganese in steel by standard additions:

I need to find the ppm of Mn in KMnO4 standard solution. Now I know the answer to this is 1119ppm however I am not sure on how to calculate this and get to the answer

mass of KMnO4 = 0.8050g and the volume of standard KMnO4 is 250ml.

Next using the ppm of 141 (initial Mn) calculate the weight % of manganese in the steel sample. the steel sample weighs 10.1347g. The answer should be 0.70 but again not sure how to get to the answer itself

I cannot figure out how to do these two calculations. I was able to solve the others just not these ones.

Any advice? Here is some other info if needed

calibration curve y= 0.0458x+0.6463

constant unknown volume = 5mL

and constant total volume = 50mL

Answer 1

Molar mass KMnO4 = 158.03 g / mole

Atomic mass Mn = 54.94 g / mol

% Mn in KMnO4 = 54.94 / 158.03 (x100%) = 34.77% Mn

ppm = mg / liter

0.8050 g KMnO4 x 34.77% Mn = 0.2799 g Mn x 1000 mg / g = 279.9 mg Mn

volume = 250 ml = 0.250 L

ppm = 279.9 mg / 0.250 L = 1119 ppm

Not sure I can help you with the remainder of the question since it isn't clear what info you have. What does 141 ppm as the "initial" Mn mean? I thought the initial Mn was 1119 ppm, at least in the standard solution of KMnO4 being used. Or is that the ppm Mn in the steel sample? Also, what good is the calibration curve if we don't have any absorbance measurements? And what does it mean by "constant" unknown and "constant" total volume?