A 0535 G Sample of Pyrolusite Ore (Impure MnO₂) Is Treated

question 75

Multiple Choice

A 0.535 g sample of pyrolusite ore (impure MnO₂) is treated with 1.42 g oxalic acid (H₂C₂O₄ ∙ 2H₂O) in an acidic medium. Following this reaction, the excess oxalic acid is titrated with 0.1000 M KMnO₄, 36.6 mL being required. What is the % MnO₂ in the ore? The reactions are: H₂C₂O₄ + MnO₂ + 2 H⁺ → Mn²⁺ + 2 H₂O + 2 CO₂
5 H₂C₂O₄ + 2 MnO₄^- + 6 H⁺ → 2 Mn²⁺ + 8 H₂O + 10 CO₂

• A) 34.4%
• B) 61.1%
• C) 2.33%
• D) 1.22%
• E) 38.9%