Chapter 9, Problem 9.22QAP

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.
Unknown,mL  Standard, mL  Absorbancc
10.0       0.0     0.201
10.0       10.0     0.292
10.0       20.0     0.378
10.0       30.0     0.467
10.0       40.0     0.554
(a) Plot the data using a spreadsheet.
(b) Determine an equation for the relationship between absorbance and volume of standard.
(c) Calculate the statistics for the least-squares relationship in (b).
(d) I)ctcrmine the conccnt ration oÍCr in ppm in the sample.
(e) Find the standard deviation of the result in (d).