The mineral rhodochrosite [manganese (II) carbonate, MnCO3] is a commercially important source of manganese. Write a half-reaction for the oxidation of the manganese in MnCO3 to MnO2 in neutral groundwater where the principal carbonate species is HCO3-. Add H2O, H+, and electrons as needed to balance the half-reaction.

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Chemistry

26 February, 11:30

The mineral rhodochrosite [manganese (II) carbonate, MnCO3] is a commercially important source of manganese. Write a half-reaction for the oxidation of the manganese in MnCO3 to MnO2 in neutral groundwater where the principal carbonate species is HCO3-. Add H2O, H+, and electrons as needed to balance the half-reaction.

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Brisa Vaughn · Answer 1

MnCO3 + 2H2O ⇄ MnO2 + HCO3 - + 2e - + 3H+

Explanation:

The unbalanced equation

MnCO3 ⇄ MnO2 + HCO3-

In MnCO3, the oxidation number of Mn is + 2

In Mno2, the oxidation number of Mn is + 4

The change from + 2 to + 4 requires an addition of 2 electrons (to the right side).

MnCO3 ⇄ MnO2 + HCO3 - + 2e-

The total charge now is - 3 on the right side. To balance this we add 3 hydrogen atoms on the right side.

MnCO3 ⇄ MnO2 + HCO3 - + 2e - + 3H+

On the right side we have 4 hydrogen atoms in total. On the left side we have 0 hydrogen atoms. So to balance, we have to add 2H2O on the left side

MnCO3 + 2H2O ⇄ MnO2 + HCO3 - + 2e - + 3H+

Now the reaction is balanced.