A 4.97-g petroleum specimen was decomposed by wet ashing and subsequently diluted to 500 mL in a

Question:

A 4.97-g petroleum specimen was decomposed by wet ashing and subsequently diluted to 500 mL in a volumetric flask. Cobalt was determined by treating 25.00-mL aliquots of this diluted solution as follows:

Assume that the Co(II)/ligand chelate obeys Beer's law and calculate the percentage of cobalt in the original sample.