Which statement describes a common natural form of manganese (Mn) in soils and is not MnO?

Which statement describes a common natural form of manganese (Mn) in soils and is not MnO?

• A. MnO
• B. Mn^+2
• C. Mn^+4
• D. MnO2

Answer: (D)

Manganese in soils most often appears as oxide minerals formed under oxidizing conditions. In these environments manganese is converted to Mn(IV) oxides, which precipitate as solid MnO2 minerals (such as pyrolusite or related forms). This MnO2 form is insoluble and controls how manganese behaves in the soil, including giving characteristic colors and persisting as a solid phase. That’s why the statement describing a common natural form of manganese in soils that is not MnO is MnO2. MnO would be a monoxide form of Mn(II) and is not typically stable or prevalent as a natural solid in soils. Mn2+ (the Mn^2+ ion) is the soluble form that dominates under reducing conditions, while Mn4+ as a general oxidation state is represented in soils specifically by MnO2 minerals rather than as a standalone MnO oxide.

Manganese in soils most often appears as oxide minerals formed under oxidizing conditions. In these environments manganese is converted to Mn(IV) oxides, which precipitate as solid MnO2 minerals (such as pyrolusite or related forms). This MnO2 form is insoluble and controls how manganese behaves in the soil, including giving characteristic colors and persisting as a solid phase.

That’s why the statement describing a common natural form of manganese in soils that is not MnO is MnO2. MnO would be a monoxide form of Mn(II) and is not typically stable or prevalent as a natural solid in soils. Mn2+ (the Mn^2+ ion) is the soluble form that dominates under reducing conditions, while Mn4+ as a general oxidation state is represented in soils specifically by MnO2 minerals rather than as a standalone MnO oxide.