A student needs 635 g of zinc sulfide, a white pigment, for an art project. He can synthesize it using the?

A student needs 635 g of zinc sulfide, a white pigment, for an art project. He can synthesize it using the reaction given below.





Na2S + Zn(NO3)2 ---%26gt; ZnS + 2NaNO3





How many grams of zinc nitrate will he need if he can make the zinc sulfide in 86.4% yield? Assume that he has plenty of sodium sulfide.

A student needs 635 g of zinc sulfide, a white pigment, for an art project. He can synthesize it using the?
Moles - you gotta know all about moles.





635 g of ZnS is how many moles? Divide by the molar mass - in this case it's about 95 g/mole but you;re going to want to make sure that you have the proper number of significant figures.





As a SWAG, this is about 6.4 moles. If you have 86.4% yield, you'll need more - divide 6.4 by 0.864. This will be a number about 7 moles or so.





For every mole of ZnS, you need one mole of Zn(NO3)2 - so you need 7 moles of the reactant, too.





Muliply by the molar mass of Zn(NO3)2 5o get the answer. (The molar mass od the nitrate is something like 169 g/mole, so the answer will be on the order of 1,200 g.