The chromium in an aqueous sample was determined by pipetting 10.0 mL of the unk

Question

The chromium in an aqueous sample was determined by pipetting 10.0 mL of the unknown into each of five 50.0-mL volumetric flasks. Various volumes of a standard containing 12.2 ppm Cr were added to the flasks, following which the solutions were diluted to volume. Plot the data. Derive an equation for the relationship between absorbance and volume of standard. Calculate the standard deviation for the slope and the standard deviation about regression in (b). Calculate the ppm Cr in the sample. Calculate the standard deviation of the result in (d).

Explanation / Answer

Plot the two pairs of points:

A vs. std.conc

And (A- first INTERCEPT) vs Std.conc

Read the first INTERCEPT 0.202 on the second plot to obtain the sample concentration in your standard sol. prepared for A measurements. It is

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