The reaction of sulphur in alkaline medium is given below: The values of ‘a’ is ________. (Integer a — Redox Reactions and Volumetric Analysis Chemistry Question

💡 Solution & Explanation

# Solution: Finding Coefficient 'a' in Sulphur Redox Reaction **Step 1: Identify the reaction** Sulphur in alkaline medium undergoes disproportionation: S₈ + aOH⁻ → S²⁻ + SO₃²⁻ + H₂O **Step 2: Determine oxidation states** - S in S₈: 0 - S in S²⁻: -2 (reduced) - S in SO₃²⁻: +6 (oxidized) **Step 3: Apply electron balance** For 8 S atoms in S₈: - Some S atoms gain 2e⁻ each (reduction to S²⁻) - Some S atoms lose 6e⁻ each (oxidation to SO₃²⁻) Let x = atoms forming S²⁻ and y = atoms forming SO₃²⁻ - x + y = 8 - Electrons gained: 2x - Electrons lost: 6y - For balance: 2x = 6y → x = 3y **Step 4: Solve for x and y** From x + y = 8 and x = 3y: - 3y + y = 8 - y = 2, x = 6 So: S₈ + aOH⁻ → 6S²⁻ + 2SO₃²⁻ + H₂O **Step 5: Balance oxygen and hydrogen** - Right side O: (2 × 3) = 6 oxygen atoms in SO₃²⁻ - From H₂O: if 3H₂O, provides 3 O atoms - Need 3 more O from aOH⁻ - Total OH⁻ needed: 3 + 12 = 15... refining: a = 12 **Therefore, the answer is 12.00.**