Final answer:
To find the required volume of C2H2 to produce 40.0 L of CO2, the mole ratio from the balanced equation (2 to 1) is used, resulting in 20.0 L of C2H2.
Step-by-step explanation:
The question involves using a balanced chemical equation to relate volumes of reactants and products in a reaction. The given equation is 2C2H2 (g) + 5O2 (g) + 2H2O (g) → 4CO2 (g). To find the volume of C2H2 required to form 40.0 L of CO2, you look at the mole ratio of CO2 to C2H2, which is 4 to 2, or simplifying it, 2 to 1. This means for every 2 volumes of CO2 produced, 1 volume of C2H2 is consumed.
Therefore, to produce 40.0 L of CO2, we would need half of that volume in C2H2. So, the answer is 40.0 L / 2 = 20.0 L of C2H2. Hence, the correct answer is (a) 20.0 L.