Lead(II) sulfide, PbS, is a compound most often purified from the mineral galena

Question

Lead(II) sulfide, PbS, is a compound most often purified from the mineral galena. PbS and other similar lead containing compounds are used as semiconductors in various analytical instruments. However, misuse of PbS is toxic and can lead to lead poisoning. a) If you have 1.00 mole of PbS how many moles of lead are present? b) Determine the weight of lead in the compound. c) Calculate the weight percent of lead in PbS. d) Assume you are given 10.0g of PbS. What mass of lead in grams is present in 10.0g of PbS?

Explanation / Answer

(a) PbS has stoichiometry of 1.

So, 1 mole of PbS contains 1 mole of lead.

(b) 1 mole of lead = weight / molar mass

molar mass of lead = 207 u

so, weight = 1 mole x 207u = 207g

(c) 1 mole of compound has weight = weight/ molar mass = weight/239.2g/mol

weight of compound PbS = 239.2 g

weight % of Pb = 207/239.2 x 100 = 86.5%

(d)no. of moles of PbS present = mass / molar mass = 10/239.2 = 0.0418moles

So, moles of Pb present = 0.0418 moles

mass of lead present = 0.0418 moles x 207 u = 8.65g

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