How many moles of Al are used to form 509.8 g of Al2O3?

1019.6 moles of Al.

Explanation:

4Al + 3O2 → 2Al2O3

You have 509.8 g moles of Al2O3. While balancing the equation, you got 2 moles of Al2O3 and 4 moles of Al,

so "4 mol Al gives 2 mol Al2O3

After you cancel out the units of measurement to check the order of the conversion, multiply 509.8 g with 4 and then divide the answer by 2.

. = (509.8 x 4) / 2

= 2039.2 / 2

= 1019.6 moles of Al.