The balanced chemical equation for the formation of water is:
\[ 2H_2 + O_2 \rightarrow 2H_2O \]
From this equation, we can see that 2 moles of hydrogen gas (H₂) react with 1 mole of oxygen gas (O₂) to produce water.
To find out how many moles of O₂ are required to react with 27.4 moles of H₂, we use the mole ratio from the balanced equation:
\[ \text{Mole ratio of } H_2 \text{ to } O_2 = 2:1 \]
This means that for every 2 moles of H₂, you need 1 mole of O₂. Therefore, to find the amount of O₂ required for 27.4 moles of H₂, you can set up the following calculation:
\[ \text{Moles of } O_2 = \frac{27.4 \text{ moles } H_2}{2} = 13.7 \text{ moles } O_2 \]
So, the answer is:
B. 13.7 mol