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# can someone help me with these empirical formula questions watch

1. 4.00g of mercury from 4.64g of mercury sulphide

0.93g of phosphorus form 2.13g of phosphorus oxide

5.60g of iron form 16.25g of iron oxide
2. (Original post by DANIELREED)
4.00g of mercury from 4.64g of mercury sulphide

0.93g of phosphorus form 2.13g of phosphorus oxide

5.60g of iron form 16.25g of iron oxide
I've moved this to the Chemistry forum where hopefully you'll get more responses
3. Okay so for each one you first need to work out the masses of each ion/element (element in these cases). Then divide the mass by the relative atomic mass of the element to get the number of moles of each element. To get the smallest whole number ratio you divide each number of moles by the smallest one. That gives you the number of moles of each element in each one.

So in the first one, you have 4g mercury and 0.64g sulfur (as sulphide ions). In moles that's 0.0199 mol sulfur and 0.0199 mol mercury, so the lowest whole number mole ratio is 1:1, and the empirical formula is HgS.

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