In the reaction 2 H2 + O2 -> 2 H2O, and given masses 5.00 g H2 and 4.00 g O2, which is the limiting reagent and what is the theoretical yield of H2O (g)?

• A. H2 is limiting; theoretical yield 4.50 g H2O.
• B. Oxygen is the limiting reagent; theoretical yield 4.50 g H2O.
• C. H2 is limiting; theoretical yield 9.00 g H2O.
• D. O2 is limiting; theoretical yield 9.00 g H2O.

Answer: (B)