One complete reaction of FeCl with oxalic acid in aqueous solution containing KOH, resulted in the f — Practical Organic Chemistry and Purification Chemistry Question

💡 Solution & Explanation

**Step 1: Identify the reactants and conditions** FeCl₃ reacts with oxalic acid (H₂C₂O₄) in aqueous KOH solution. The alkaline medium converts oxalic acid to its conjugate base (oxalate ion, C₂O₄²⁻). **Step 2: Determine the oxidation state of Fe in product A** In the presence of oxalate and KOH, Fe³⁺ is reduced to Fe²⁺ by oxalic acid. Product A is a potassium ferrous oxalate complex: K₂[Fe(C₂O₄)₂]·2H₂O or K₃[Fe(C₂O₄)₃] **Step 3: Identify the likely product** The most common product is K₃[Fe(C₂O₄)₃], where Fe is in the +3 oxidation state, and three oxalate ligands (bidentate) coordinate to Fe. **Step 4: Count the coordination number** Each oxalate ion (C₂O₄²⁻) is a bidentate ligand, bonding through two oxygen atoms. - Number of oxalate ligands = 3 - Coordination number = 3 × 2 = 6 **Step 5: Relate coordination number to secondary valency** Secondary valency refers to the coordination number—the total number of ligand donor atoms bonded to the central metal ion. Therefore, the answer is **6.00**.