
This is generally an intermediate reaction in a permanganate test for chloride ion.
Write the half-reaction skeletons.
MnO2(s)→Mn2+(aq)
Cl−(aq)→Cl2(g)
- You explicitly stated the oxidation state of Mn in both compounds, so it should be obvious that manganese got reduced.
- Chlorine gas is a homonuclear diatomic, and therefore has an oxidation state that changed from −1 in Cl− to zero in Cl2.
Now, to balance them,
- Balance non-O and non H atoms.
- Add H2O to balance O atoms, since we are in aqueous conditions.
- Add H+ to balance H atoms, since we are in acidic conditions.
- Add e− to balance charge, as a formal way to depict change in oxidation state.
