20 mL of 0.02 M K Cr O solution is used for the titration of 10 mL of Fe solution in the acidic medi — Redox Reactions and Volumetric Analysis Chemistry Question

💡 Solution & Explanation

# Solution: Titration of Fe²⁺ with K₂Cr₂O₇ **Step 1: Write the balanced redox equation** In acidic medium, K₂Cr₂O₇ oxidizes Fe²⁺: - Cr₂O₇²⁻ + 6Fe²⁺ + 14H⁺ → 2Cr³⁺ + 6Fe³⁺ + 7H₂O **Step 2: Identify the mole ratio** From the balanced equation: - 1 mol K₂Cr₂O₇ : 6 mol Fe²⁺ - Or: n(Cr₂O₇²⁻) : n(Fe²⁺) = 1 : 6 **Step 3: Calculate moles of K₂Cr₂O₇** n(K₂Cr₂O₇) = Molarity × Volume n(K₂Cr₂O₇) = 0.02 M × 0.020 L = 4 × 10⁻⁴ mol **Step 4: Calculate moles of Fe²⁺ using stoichiometry** n(Fe²⁺) = 6 × n(K₂Cr₂O₇) n(Fe²⁺) = 6 × 4 × 10⁻⁴ = 2.4 × 10⁻³ mol **Step 5: Calculate molarity of Fe²⁺ solution** Molarity = moles/Volume (in L) Molarity = (2.4 × 10⁻³)/(0.010) = 0.24 M = 24 × 10⁻² M Therefore, the answer is 24.