Question

A:For this question, assume the vitamin sample solution put into the spectrophotometer had an absorbance reading of 0.248, and the equation of the best-fit line from the calibration curve was y = 420 (x) + 0.00001 . What is the concentration of Fe2+ in the vitamin solution that was put into the spectrophotometer.

B:Assume that the known Fe solution that was put into the spectrophotometer was determined to have an Fe concentration of 0.0035 mg/mL . Follow the calculations on page 6 of Experiment 22 to calculate the mg Fe in the orginal Fe sample used (calc. step 1).

Answer 1

With no more details than those given I'm out on a limb here. I assume that the best fit line fits the equation A = ebc where e is the molar absorptivity constant = 420, y is Absorbance, I asume c you want in moles/L and b is the path length which I assume is 1 cm.
y = 420 (x) + 0.00001
1.
0.248 = 420 X + 0.00001. I assume X = concentration and usually that is measured in moles/L and I assume you want to calculate concentration in moles/L. So figure away and solve for X = C. However, since part B gives concentration in mg/mL I may not have assumed correctly.
When we go to part B of your question I have no idea what page 6 of experiment 22 is. Sorry about that.
You just don't give enough definitive information to help me help you.