Volume of Sample Taken, 4 μM Pb2+ 20 0 50 5 Reagent Volumes Used, mL Absorbance, A, 545 nm Ligand 20 water 10 0.2 20 5 0.8 Calculate the concentration of lead in the sample.

^{A 5.0-g pesticide sample was decomposed by wet ashing and then diluted
to 200.0 mL in a volumetric flask. The analysis was completed by treating aliquots of
this solution as indicated. It has known that only the chelate PbL}4^{2- will absorb light at
wavelength 545 nm and has a linearly calibration curve in a wide range of concentration.
Assume the concentration of ligand is far more than that of lead in each measurement so
that all the lead will be react with the ligand to form chelate.}