Potassium permanganate solutions used in oxidation-reduction titrations are sometimes standardized against Fe²⁺ ion. The reaction involved is 8H⁺(aq) + MnO₄⁻(aq) + 5Fe²⁺(aq) → 5Fe³⁺(aq) + Mn²⁺(aq) + 4H₂O(l).
Potassium permanganate solutions used in oxidation-reduction titrations are sometimes standardized against Fe²⁺ ion. The reaction involved is
8H⁺(aq) + MnO₄⁻(aq) + 5Fe²⁺(aq) → 5Fe³⁺(aq) + Mn²⁺(aq) + 4H₂O(l).
A convenient source for Fe²⁺ ion is ammonium iron(II) sulfate, (NH₄)₂Fe(SO₄)₂(H₂O)₆ (FW = 392.14), also known as Mohr's salt, which is readily crystallized, and the crystals resist oxidation by air. A 0.6735 g sample of Mohr's salt is dissolved in 100 mL of acid solution, and the permanganate solution is added slowly from a buret. The endpoint is reached when 17.86 mL of the permanganate solution has been added.
Calculate [MnO₄⁻], the molar concentration of the permanganate solution.
Note: 0.0461 M and 0.0462 M are incorrect
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