### Correct Option: B. 4 moles ### Detailed Explanation: To determine how many moles of water (H₂O) are produced from 4 moles of hydrogen gas (H₂) reacting with excess oxygen (O₂), we need to analyze the balanced chemical equation provided: **Balanced Equation:** \[ 2 \text{H}_2 + \text{O}_2 \rightarrow 2 \text{H}_2\text{O} \] #### Step 1: Understand the Stoichiometry The coefficients in a balanced chemical equation represent the ratio in which reactants combine and products form. In this equation: - 2 moles of hydrogen gas (H₂) react with 1 mole of oxygen gas (O₂) to produce 2 moles of water (H₂O). This means: - For every 2 moles of H₂, 2 moles of H₂O are produced. - Therefore, the ratio of H₂ to H₂O is 1:1. #### Step 2: Calculate the Moles of Water Produced Now, we have 4 moles of hydrogen gas (H₂). To find out how many moles of water (H₂O) are produced, we can set up a proportion based on the stoichiometry of the reaction: - From the balanced equation, we see that 2 moles of H₂ produce 2 moles of H₂O. - Thus, if we have 4 moles of H₂, we can calculate the moles of H₂O produced as follows: \[ \text{Moles of H₂O} = \text{Moles of H₂} \times \left(\frac{2 \text{ moles of H₂O}}{2 \text{ moles of H₂}}\right) \] Substituting the values: \[ \text{Moles of H₂O} = 4 \text{ moles of H₂} \times \left(\frac{2 \text{ moles of H₂O}}{2 \text{ moles of H₂}}\right) = 4 \text{ moles of H₂O} \] Thus, 4 moles of hydrogen gas will produce 4 moles of water. ### Step 3: Analyze the Other Options Now, let’s look at the other options and explain why they are incorrect: - **Option A: 2 moles** - This option suggests that only 2 moles of water are produced. This is incorrect because, according to the stoichiometry of the reaction, 4 moles of H₂ should yield 4 moles of H₂O, not just 2. - **Option C: 6 moles** - This option implies that 6 moles of water are produced. This is incorrect as it does not follow the stoichiometric ratio from the balanced equation. The reaction does not produce more water than the amount of hydrogen available. - **Option D: 8 moles** - This option suggests that 8 moles of water are produced. This is also incorrect because it exceeds the amount of hydrogen available. The maximum amount of water that can be produced is limited by the amount of hydrogen gas present, which is 4 moles. ### Summary of Key Points: - The balanced equation shows that 2 moles of H₂ produce 2 moles of H₂O, establishing a 1:1 ratio. - With 4 moles of H₂, the reaction produces 4 moles of H₂O. - The other options (A, C, D) do not adhere to the stoichiometric ratios from the balanced equation. ### Revision Summary: - Always refer to the balanced chemical equation to determine the stoichiometric ratios. - Use the ratios to calculate the amount of product formed based on the amount of reactant available. - Remember that the limiting reactant (if present) will dictate the maximum amount of product formed. - Practice with different amounts of reactants to reinforce understanding of stoichiometry.