Question about calculating moles in CHEM?

Question

How do I determine the following?

How many moles of PBCO3 are there in 7.5g of the starting material?

Answer 1

Your question does not make sense. What is the starting material you were given? What reactions did you perform to get there? Do you mean PbCO3 (Lead carbonate) or the factitous Phosphoboro carbonate (PBCO3)?

If you are looking for how many moles of lead carbonate are in 7.5 grams: take the molecular weight of each atom (Pb, C, O) and multiply it by the subscript (i.e. 3 for O) and sum them up. This is the weight of one mole of lead carbonate. To determine the number of moles, divide 7.5g by the molecular weight.