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A 0.5 M aqueous solution of KMnO4 is split into two portions. The first portion reacts completely with 125 mL of a 1.5 M oxalate ion solution in acidic medium. The second portion reacts completely with 270 mL of a 0.5 M iodide ion solution in neutral medium, where iodide is oxidised only to I2. Find the total volume (in mL) of the original KMnO4 solution.
- 250 mL
- 500 mL
- 750 mL
- 1000 mL
Correct answer: 250 mL
Solution
In acidic medium MnO4⁻ is reduced to Mn²+ (n-factor = 5) and oxalate is oxidised to CO2 (n-factor = 2 per C2O4²-). In neutral medium MnO4⁻ is reduced to MnO2 (n-factor = 3) and I⁻ is oxidised to I2 (n-factor = 1). Applying meq balance gives total KMnO4 volume of approximately 240 mL, closest to 250 mL.
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