If 300.0 grams of FeCr2O7 react, how many grams of O2 will be consumed

You are given 300 grams of FeCr2O7. You are required to get the mass of O2 in grams. The first thing to do is to find a reaction between FeCr2O7 and O2. The balanced chemical reaction is 2Fe + 6Cr + 21/2O2 - > Fe2 (Cr2O7) 3. The molar mass of Fe2 (Cr2O7) 3 is 759.65 grams per mole and 32 grams per mole for O2.

300g Fe2 (Cr2O7) 3 (1 mol Fe2 (Cr2O7) 3/759.65 g Fe2 (Cr2O7) 3) (21/2 mol O2/1 mole Fe2 (Cr2O7) 3) (32 g O2/1 mole O2) = 132.7 g O2