Question

An ionic compound is found to contain 10.9% magnesium, 31.8% chlorine and 57.3% oxygen. What is the empirical formula for this compound?

Answer 1

In a 100.g sample of the compound, there would be 10.9g Mg, 31.8g Cl, and 57.3g O. Therefore, there are ~.45 mol Mg, ~.90 mol Cl, and ~3.58 mol O. You then divide all the numbers by 0.45 mol, so you get 1 mol of Mg for every 2 mol of Cl for every 8 mol of O. So the empirical formula would be MgCl2O8.