Final answer:
To form 817 g of Fe₃O₄ with a reaction yield of 68.2%, approximately 265.29 g of iron must react with excess steam.
Step-by-step explanation:
To determine the amount of iron needed to form 817 g of Fe₃O₄, we need to find out the molar mass of Fe₃O₄. Fe has a molar mass of 55.845 g/mol and O has a molar mass of 15.999 g/mol.
So the molar mass of Fe₃O₄ is (3 × 55.845) + (4 × 15.999) = 231.532 g/mol.
Since the reaction yield is 68.2%, we can calculate the amount of iron needed as follows:
Amount of Fe = (mol of Fe₃O₄ × molar mass of Fe₃O₄) / reaction yield
Amount of Fe = (817 g ÷ 231.532 g/mol) / 0.682 = 4.75 mol
Now, we can calculate the mass of iron needed:
Mass of Fe = mol of Fe × molar mass of Fe = 4.75 mol × 55.845 g/mol = 265.29 g