What mass of CO reacts with 25.13 g of Fe2O3 according to Fe2O3 + 3CO giving 2Fe + 3CO2?

1. Both the quantity given and the quantity wanted are masses of reactants. 2. First convert 25.13 g of Fe2O3 to moles using its molar mass. 3. Apply the stoichiometric factor, which is 3 mol CO per 1 mol Fe2O3. 4. Convert the resulting moles of CO back to a mass using the molar mass of CO. 5. Working the chain through gives 13.22 g of CO. 6. Dividing rather than multiplying by 3 gives 4.41 g, which is the reversed-factor trap. 7. Equal masses are never assumed, because the two substances have different molar masses. _Source: OpenStax Chemistry (CC BY 4.0), Ch 4 "Stoichiometry of Chemical Reactions", section 4.3 Reaction Stoichiometry_