The question requires us to calculate the number of moles of each element (magnesium, chlorine and oxygen) in 8.30 moles of the compound magnesium perchlorate (Mg(ClO4)2).
From the molecular formula of magnesium perchlorate we can take the following information:
- in 1 mol of Mg(ClO4)2, there is only 1 mol of Mg;
- in 1 mol of Mg(ClO4)2, there are 2 moles of Cl;
- in 1 mol of Mg(ClO4)2, there are 8 moles of O.
With the information above, and knowing that the amount of Mg(ClO4)2 given by the question was 8.30 moles, we can calculate the amount, in moles, of each element:
1 mol Mg(ClO4)2 --------------- 1 mol Mg
8.30 mol Mg(ClO4)2 ---------- x = 8.30 mol Mg
1 mol Mg(ClO4)2 --------------- 2 mol Cl
8.30 mol Mg(ClO4)2 ---------- y = 2 x 8.30 mol Cl = 16.6 mol Cl
1 mol Mg(ClO4)2 --------------- 8 mol O
8.30 mol Mg(ClO4)2 ---------- z = 8 x 8.30 mol O = 66.4 mol O
Therefore, there are 8.30, 16.6 and 66.4 moles of Mg, Cl and O in 8.30 moles of magnesium perssufate.