Homework Help: Chemistry

Posted by Lance on Wednesday, April 4, 2012 at 12:59am.

A mixture of the compounds magnesium oxide and calcium sulfide contains 21.6999 g of magnesium oxide and is 51.3 % by mass magnesium oxide. The compound calcium sulfide is 44.400 % by mass sulfur. Calculate the moles of sulfur in the mixture.

I'm not sure what I did wrong.
My attempt:
21.6999g CaS2 / molar mass of CaS2 = 0.30079 mol

Answer: 0.285246979573 mol.

Thanks.

Chemistry - DrBob222, Wednesday, April 4, 2012 at 1:32am
21.9999/0.513 = total grams mixture
grams mixture x (1.00-0.487) = g CaS
grams CaS/molar mass CaS = mols CaS
mols S = mols CaS.

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