Problem 4.110 Lead glass contains 18-40% by mass of PbO (instead of CaO in regul

Question

Problem 4.110 Lead glass contains 18-40% by mass of PbO (instead of CaO in regular glass). Lead glass is still used industrially, but lead crystal drinking goblets are no longer considered safe, as the lead may leach out and cause toxic responses in humans. A particular 266-g lead crystal goblet that holds 500 mL of liquid is 31 % PbO by mass, and it leaches 4.4 micrograms of lead every time it is filled. Part A How many grams of sodium sulfide would be required to decontaminate all the lead in the entire goblet? Express your answer using two significant figures.

Explanation / Answer

= 266 g of leat

V = 500 mL

x = 0.31 of PbO

m = 4.4 micrograms per fill

m = 4.4*10^-6 micrograms of Pb

so

PbO --> Pb+2 + O2- in solution

then

mol of Pb = mass/MW = (44*10^-6) / 207.2 = 2.123*10^-7 mol of Pb+2

so...

we need

Na2S + Pb+2 = PbS(s) + 2Na+

so..

1:1 ratio

2.123*10^-7 mol of NA2S per 2.123*10^-7 mol o fPB+2

mass of Na2S = mol*MW = (2.123*10^-7 )*78.0452 = 0.00001656899 g of Na2S are required

1.7*10^-5 g of Na2S ( 2 sig fig)

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