This question is a way to review reaction stoichiometry calculation when only the amount of one reactant is given.
You are given the balanced equation (if you were not you would need to balance it first). This equation is telling you that for every 2 moles of O2 used 3 moles of Fe is needed and 1 mol of Fe3O4 is formed.
In any stoichiometric calculation we use the stoichiometric relationship from balanced equations to relate the reactants and products together.
You should know how to calculate the molar mass of a substance [ Molar mass of Fe3O4= 231.6 g/mol ] and # mol moles of a substance [divide by its molar mass].
a) mols O2 reacting = 6.53 * (1mol O2 /32.0 g O2) = 0.204 mol
Using the stoichiometric relationship from the balanced equation:
b) mols of Fe needed = mol O2 reacting * (3 mol Fe / 2 mol O2 ) = 0.306 mol
c) mols of Fe3O4 formed = mol O2 reacting * (1 mol Fe3O4 / 2 mol O2 ) = 0.102 mol
d) mass of Fe3O4 = mols Fe3O4 * ( Molar mass of Fe3O4 /1 mol Fe3O4) = 23.6 g
With this information you should be able to get the answers and also work future problems. Answers are given to 3 sig. fig because of the # of sig fig given in the question...
Hope this helps for future calculations as well!
