What are the empirical formulas of substances with the following ...

Question

What are the empirical formulas of substances with the following mass percent compositions? 
(b) Ilmenite (a titanium-containing ore): 31.63% O, 31.56% Ti, 36.81% Fe

Accepted Answer

Hey everyone. Our question here is asking us to provide the correct empirical formula for a substance containing 5.51% lithium 43.64% manganese and 50.84% oxygen. A key to this question is to recognize that we have 100% of our compound present. So we can go ahead and assume that we have 100 g and this will make it easier for us to convert from percentages into grams. Starting off with lithium, we have 5.51 g of lithium and we want to convert all of our grams into moles. Looking at our periodic table, we can see that we have 6.94 g of lithium per one mole of lithium. And when we calculate this out, we end up with a total of 0.7939 mol of lithium. Moving on to Manganese, we have 43.64 g of manganese. And we can see that Manganese has an atomic mass of 0.94 grams per one mole Calculating this out, we end up with a total of 0.7943 mol of manganese. Next looking at oxygen, we have 50.84g of oxygen And we know that oxygen has a molar mass of 16.0 g per one mole. When we calculate this out, we end up with a total of 3.1775 mole of oxygen. In order to find our empirical formula, we're going to need to divide each value by the least amount of moles we have listed here, and in this case it's going to be lithia. So dividing each value by 0.7939, we end up with one of lithium, Approximately one of manganese and approximately four of oxygen. So our empirical formula is going to be LIMN 04, and this is our final answer. So I hope this made sense and let us know if you have any questions.

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