To determine the quantity of electricity required to liberate 0.125 moles of oxygen molecules during the electrolysis of dilute sodium chloride solution, we need to follow a systematic approach. Let's break it down step-by-step. ### Step 1: Understanding the Electrolysis Reaction During the electrolysis of dilute sodium chloride (NaCl) solution, water is also present, and the following half-reaction occurs at the anode (where oxidation takes place): \[ 2 \text{H}_2\text{O} \rightarrow \text{O}_2 + 4 \text{H}^+ + 4 \text{e}^- \] This equation tells us that to produce 1 mole of oxygen gas (O₂), 4 moles of electrons (e⁻) are required. ### Step 2: Calculate Moles of Electrons Needed Since we want to liberate 0.125 moles of O₂, we can calculate the moles of electrons needed using the stoichiometry of the reaction: - For 1 mole of O₂, 4 moles of electrons are needed. - Therefore, for 0.125 moles of O₂: \[ \text{Moles of electrons} = 0.125 \, \text{moles O}_2 \times 4 \, \text{moles e}^- / \text{mole O}_2 = 0.5 \, \text{moles e}^- \] ### Step 3: Convert Moles of Electrons to Charge Now, we need to convert the moles of electrons into coulombs (the unit of electric charge). We use Faraday's constant (F), which is the charge of one mole of electrons: \[ F = 96,500 \, \text{C/mol} \] To find the total charge (Q) in coulombs, we use the formula: \[ Q = \text{moles of electrons} \times F \] Substituting the values we have: \[ Q = 0.5 \, \text{moles e}^- \times 96,500 \, \text{C/mol} = 48,250 \, \text{C} \] ### Step 4: Final Answer Thus, the quantity of electricity required to liberate 0.125 moles of oxygen molecules during the electrolysis of dilute sodium chloride solution is: **B. 48,250 coulombs** ### Step 5: Explanation of Other Options - **Option A (24,125 coulombs)**: This value is half of the correct answer. It likely results from a misunderstanding of the stoichiometry, possibly calculating for only 0.0625 moles of O₂ instead of 0.125 moles. - **Option C (72,375 coulombs)**: This value is too high and suggests that the calculation may have incorrectly doubled the required moles of electrons or misapplied Faraday's constant. - **Option D (96,500 coulombs)**: This value corresponds to the charge needed for 1 mole of electrons (which would liberate 0.25 moles of O₂), not the 0.125 moles specified in the question. ### Revision Summary - The electrolysis of water produces oxygen at the anode, requiring 4 moles of electrons for every mole of O₂ produced. - For 0.125 moles of O₂, 0.5 moles of electrons are needed. - The total charge can be calculated using Faraday's constant: \( Q = \text{moles of electrons} \times F \). - The correct answer is 48,250 coulombs, corresponding to option B.