Galena(PbS) and cerussite(PbCO3)are two ores of lead. A mining company is considering which of these two ores to use for the extraction of lead.

Question

The equations for the reactions occurring are

process using galena:

2PbS+3O2 ---> 2PbO+2SO2

2PbO+C ----> 2Pb+CO2

Process using cerussite:

PbCO3--->PbO+CO2

2PbO+c--->2Pb+CO2

The company uses a sample of cerussite containing 500g of PbCO3
Calculate the maximum mass of lead that can be obtained from this sample of cerussite. (3 marks)

Mass of lead=.............................g

Answer 1

mols PbCO3 = grams/molar mass
Convert mols PbCO3 to mols PbO using the coefficients in the first balanced equation.
Convert mols PbO to mols Pb in the second balanced equation.
Now convert mols Pb to g Pb. g = mols x atomic mass.

You can do all of the conversions at once if you wish and save some time.
mols PbCO3 x (1 mol PbO/1 mol PbCO3) x (2 mol Pb/2 mols PbO) = ?
Then convert mols Pb to grams.

Answer 2

500/207+12+(16x3) = 1.87

1.87x207 = mass of lead from PbCO3 = 387.09 g