The formula for rust can be represented by Fe2O3. How many moles of Fe are present in 25.7 g of the compound?

Question

whpalmer4 · Answer

$$\text{Fe}_2\text{O}_3$$means that each molecule has 2 iron atoms and 3 oxygen atoms.  Look up the atomic mass of iron and oxygen on your periodic table, multiply by 2 and 3 respectively and add to get the molar mass of the compound.  Now you have a simple proportion problem to solve.  Number of grams of compound / molar weight of compound gives you the number of moles of the compound.  To get moles of Fe, you multiply by 2 because there are 2 moles of Fe atoms per mole of compound.

anonymous · Answer

So I should get .322 mol?

whpalmer4 · Answer

well, 159.69 g/mol is the molar mass of Fe2O3

We have 25.7 g of Fe2O3, so that gives us $$\frac{25.7}{159.69}\text{moles Fe}_2\text{O}_3 = 0.161 \text{ moles Fe}_2\text{O}_3$$and remembering that 1 mole of Fe2O3 contains 2 moles of Fe, that gives us 0.322 mole Fe.