acetylélle l EXERCISE 9.8: The method of standard addition was used determine th

Question

acetylélle l EXERCISE 9.8: The method of standard addition was used determine the amount of iron in a sample of water by DCP-AES. The data collected are presented in the table and the dark current for the spectrometer was 2.9 to Added Fe Detector (ug/L) Output (mA) p) 5.9 11.0 16.1 10 (a) Use a spreadsheet to plot a least squares regression line through the data. Be certain to display the x intercept on your graph. Also, display the equation for your line and the correlation coefficient on your graph. Determine the concentration of iron in the original sample and use the standard deviation of your line to determine the 95% confidence limit. (b) the correct answer was actually 2.81 ppb, what is he relative error in your analysis technique? Is the eror most likely systematic or experimental? Explain your reasoning.

Explanation / Answer

Answer:

From the data

with Cx and Cs be concentration of Fe in unknown and standard

Dx and Ds be detector output for unknown and standard

using,

Cx/(Cx + Cs) = Dx/(Dx + Ds)

Cx/(Cx + 5) = 5.9/11

11x = 5.9x + 29.5

x = 5.78 ug/L

So,

concentration of iron in the unknown sample of water = 5.78 ug/L

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