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What volume (in litres) of acidified KMnO4 solution of molarity M is required to just oxidize 1 litre of a saturated solution of CaC2O4? (Ksp of CaC2O4 = 2.5 * 10⁻⁷). Assume the volume of KMnO4 needed is expressed as a ratio relative to some reference. Given the options are numerical values of volume in litres of KMnO4 solution of a specific concentration needed, find the correct answer.
- 0.1
- 0.2
- 1
- 2
Correct answer: 0.1
Solution
From Ksp: s² = 2.5e-7 => s = 5e-4 M = [C2O4²-]. Moles of C2O4²- in 1 L = 5e-4 mol. Reaction: 2KMnO4 + 5CaC2O4 + 8H2SO4 -> 2MnSO4 + 5CaSO4 + K2SO4 + 10CO2 + 8H2O. Mole ratio MnO4⁻: C2O4²- = 2:5. Moles of KMnO4 = (2/5)*5e-4 = 2e-4 mol. If KMnO4 concentration is 2e-3 M (0.002 M), volume = 2e-4/0.002 = 0.1 L. Answer = 0.1 L. The question likely specifies a particular concentration for KMnO4 solution, and the answer is 0.1.
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