Question

The formula for rust can be represented by Fe2O3 How many moles of Fe are present in 14.2 g of the compound?

Answer 1

molar mass of compound is = 56×2 + 16×3 = 160. moles of this compound = 14.2/160. there 2 moles of fe per mole of compound therefore moles of fe = 28.4/160

Answer 2

The molar mass of Fe2O3 = 2 x Fe (2 x 55.85) + 3 x O (3 x 16.00) = 159.7 g/mole.

31.0 g Fe2O3 x (1 mole Fe2O3/159.7 g Fe2O3) = 0.194 moles Fe2O3. In the recipe Fe2O3, there are 2 Fe.

So 1 mole of the compound Fe2O3 contains 2 moles of Fe. 0.194 moles Fe2O3 x (2 mole Fe/1 mole Fe2O3) = 0.388 moles Fe.