Final answer:
To react completely with 4.0 moles of propane (C3H8), 20 moles of oxygen (O2) are necessary, as per the stoichiometric ratio of the balanced chemical reaction.
Step-by-step explanation:
To determine how many moles of oxygen are necessary to react completely with 4.0 moles of propane (C3H8), we refer to the balanced chemical equation:
C3H8 + 5O2 → 3CO2 + 4H2O
According to the stoichiometry of the equation, 1 mole of propane reacts with 5 moles of oxygen. Therefore, if we have 4.0 moles of propane, we will need:
4.0 moles C3H8 × (5 moles O2 / 1 mole C3H8) = 20 moles O2
Thus, 20 moles of oxygen are necessary to completely react with 4.0 moles of propane.