when 6.25 grams of pure irons are allowed to react with oxygen, a black oxide forms. if the product weighs 8.15 g what is the empirical formula of the oxide?
Fe = 6.25 g
O = 8.15-6.25 = 1.9 g
mols Fe = 6.25/55.85 = 0.112
mols O = 1.9/16 = 0.119
So that is 1:1 or FeO for the formula.