When 10 mL of an aqueous solution of KMnO was titrated in acidic medium, equal volume of 0.1 M of an aqueous solution of ferrous sulphate was required for complete discharge of colour. The strength of

Question

When 10 mL of an aqueous solution of KMnO was titrated in acidic medium, equal volume of 0.1 M of an aqueous solution of ferrous sulphate was required for complete discharge of colour. The strength of KMnO in grams per litre is ________ × 10 . (Nearest integer) [Atomic mass of K = 39, Mn = 55, O = 16] 4 4 –2

Prashant Kotian · Accepted Answer

Correct answer: 316.00. **Step 1: Write the balanced redox equation** In acidic medium: - MnO₄⁻ + 5e⁻ → Mn²⁺ (reduction) - Fe²⁺ → Fe³⁺ + e⁻ (oxidation) Balanced equation: MnO₄⁻ + 5Fe²⁺ + 8H⁺ → Mn²⁺ + 5Fe³⁺ + 4H₂O **Step 2: Apply the titration relationship** At equivalence point: n(MnO₄⁻) × 5 = n(Fe²⁺) × 1 Since equal volumes (10 mL each) are used: Molarity of KMnO₄ × 5 = 0.1 × 1 Molarity of KMnO₄ = 0.1/5 = 0.02 M **Step 3: Calculate moles of KMnO₄** Moles = Molarity × Volume (in L) Moles = 0.02 × 0.01 = 0.0002 mol **Step 4: Calculate molar mass of KMnO₄** Molar mass = 39 + 55 + (16 × 4) = 39 + 55 + 64 = 158 g/mol **Step 5: Calculate mass and concentration** Mass of KMnO₄ = 0.0002 × 158 = 0.0316 g Strength (g/L) = (0.0316 g)/(0.01 L) = 3.16 g/L **Step 6: Express in required form** 3.16 = 316 × 10⁻² Therefore, the answer is **316.00**.

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