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 286-g lead crystal goblet that holds 550 ml of liquid is 19 % pbo by mass, and it leaches 4.2 micrograms of lead every time it is filled.

Base on my research and further investigation about the said problem, the possbile answer would be this one. 

1. calculate the g of PbO in the 272 g lead crystal (19% PbO) 272 g x 19 /100 = xxx g PbO xxx g PbO/molecular mass of PbO = moles PbO
 2. write and balance the equation of neutralization of PbO and sodium sulfide. PbO + sodium sulfide -> sodium oxide + lead sulfide
 3. Calculate the moles of sodium sulfide that will react with the moles of PbO
4. Convert the moles of sodium sulfide to g of sodium sulfide

The answer is c) pyrite