3) Tabulate the absorbance (measured at the wavelength of maximum absorbance) measured three times for each of the standards and the unknown. For each solution, calculate its average absorbance. I am not sure how to calculate its average absorbance?
(4) Graph the calibration curve, average absorbance vs. concentration in ppm Fe. Draw the straight line that best fits these data. You may use Excel to draw a "trendline" to accomplish this. (Should the line go through the origin? Explain why or why not in your report.) Visually determine (and report) the concentration of the unknown determined from the straight line. REMEMBER TO CONSIDER YOUR SAMPLE PREPARATION STEPS IN THIS CALCULATION.
(5) Also, determine the concentration of your unknown by calculation from the fitted calibration curve. How well do these agree? Be sure that the Excel trendline reports enough significant figures/decimal places for the slope and intercept to enable you to calculate your unknown concentration with at least as many significant figures as your standards. If not, use SLOPE and INTERCEPT to get more. PLEASE GIVE ME SOME DIRECTION!!!!
10 -0.0205178 -0.0052847
0 0.00499193
0.5 0.03033099
0.5 0.02218345
0.5 0.05680128
10 0.06360067
10 0.06678531
10 0.06278707
2.5 0.16393888
2.5 0.18170881
2.5 0.16184526
50 0.32504085
50 0.35915126
50 0.31992282
5 0.301783
50 0.28393507
50 0.28538445
0.4
0.35
y = 0.0628x + 0.0016
0.2 ABSORBANCE AT 396.2
0.2
0.15 ABSORBANCE
0.1
0.05
-0.05
CONCENTRATION PPM