When 10 mL of an aqueous solution of ions was titrated in the presence of dil. using diphenylamine indicator, 15 mL of 0.02 M solution of was required to get the end point. The molarity of the solutio

Question

When 10 mL of an aqueous solution of ions was titrated in the presence of dil. using diphenylamine indicator, 15 mL of 0.02 M solution of was required to get the end point. The molarity of the solution containing ions is . The value of x is __________. (Nearest integer)

Prashant Kotian · Accepted Answer

Correct answer: 18.00. **Step 1: Identify the reaction** This is a redox titration of dichromate ions (Cr₂O₇²⁻) with Fe²⁺ using diphenylamine indicator in dilute acid. The balanced equation is: Cr₂O₇²⁻ + 6Fe²⁺ + 14H⁺ → 2Cr³⁺ + 6Fe³⁺ + 7H₂O **Step 2: Determine the mole ratio** From the balanced equation: 1 mol Cr₂O₇²⁻ reacts with 6 mol Fe²⁺ Mole ratio = n(Fe²⁺) : n(Cr₂O₇²⁻) = 6 : 1 **Step 3: Calculate moles of dichromate** n(Cr₂O₇²⁻) = M × V = 0.02 M × 15 mL = 0.3 mmol **Step 4: Calculate moles of Fe²⁺** Using the mole ratio: n(Fe²⁺) = 6 × n(Cr₂O₇²⁻) = 6 × 0.3 = 1.8 mmol **Step 5: Calculate molarity of Fe²⁺ solution** M(Fe²⁺) = n/V = 1.8 mmol / 10 mL = 0.18 M **Step 6: Find x** The molarity is 0.18 M, so x = 0.18 To nearest integer: x × 100 = 18.00 Therefore, the answer is **18.00**.

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