How many atoms of iron will be produced from the reaction of 50 g of hematite and 25 g of carbon?
This is a limiting reagent (LR) problem. You know that because amounts are given for BOTH reactants.
Fe3O4 + 2C ==> 2CO2 + 3Fe
mols Fe3O4 = grams/molar mass = ?
mols C = grams/molar mass = ?
Using the coefficients in the balanced equation, convert mols Fe3O4 to mols Fe.
Do the same for mols C to mols Fe.
It is likely the two values will not agree which means one of them is not right; the correct value in LR problems is ALWAYS the smaller one and the reagent responsible for that value is the LR.
Using the smaller value convert that atoms Fe. Remember 1 mol Fe contains 6.02E23 atoms Fe