Chem 208 Quiz #3

1. (15 pt.) Rust is formed from the reaction of iron and oxygen. Once common form of rust is Fe₂O₃.

Fe + O₂ → Fe₂O₃

If I have a 1.5 kg iron rod, what mass of oxygen would be required to completely oxidize the iron? What would be the mass of the resulting iron oxide?

Answer:

First you need to balance the equation.

4 Fe + 3 O₂ → 2Fe₂O₃

Then it is all just stoichiometry:

1.5 kg Fe * 1000 g Fe * 1 mol Fe * 3 mol O₂ * 32.0 g O₂ = 645 g O₂

1 kg Fe 55.845 g Fe 4 mol Fe 1 mol O₂

1.5 kg Fe * 1000 g Fe * 1 mol Fe * 2 mol Fe₂O₃ * 159.7 g Fe₂O = 2145 g Fe₂O₃

1 kg Fe 55.845 g Fe 4 mol Fe 1 mol Fe₂O₃