I need help solving this problem, It would be greatly appreciated to show all st

Question

I need help solving this problem, It would be greatly appreciated to show all steps, i am completely lost.

Nitrate levels in well water can be determined spectrophotometrically through a procedure that measures the intensity of light absorbed at 410 nm. An unknown sample of 25.0 mL of well water was analyzed at 410 nm in a 1.00 cm cell and found to have an absorbance value of 0.721. A standard solution of nitrate with a concentration of 2.0 ppm provided an absorbance of 0.840.
a. Using Beer’s Law calculate the concentration of nitrate in the unknown sample.
b. Assuming that the instrument used in this determination could reliably detect absorbance values down to 0.05 (and that no components other than the analyte had appreciable absorbance) what would be the lower limit of detection?

Explanation / Answer

a)Both the samples that is unknown well water & nitrate are analyzed at 410 nm
for absorbances that are measured/predicted at the same Wavelength
     C1 / C2 = A1 / A2
   C1 = (0.721 / 0.840) * 2 ppm = 1.7167 ppm
concentration of Nitrate in unknown sample = 1.7167ppm
b)
   For a signal at the lower limit of detection, the error is 50% for a sample
50 = (x /0.05 ) *100 will give you lower limit of detection
Lower L.O.D = 0.025

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