(The reactant substance) has been oxidized / reduced to (the product substance).
The oxidation state of (the element) increased / decreased from (o.s. no.) in (the reactant substance) to (o.s. no.) in (the product substance).
Examples:
Explain whether the underlined substance has been oxidized or reduced, in terms of oxidation state.
1. ZnO (s) + C (s) -> Zn (s) + CO (g)
Zinc oxide has been reduced to zinc.
The oxidatation state of zinc decreased from +2 in zinc oxide to 0 in zinc.
2. PbS (s) + 4H2O2 (aq) -> PbSO4 (s) + 4H2O (l)
Lead(II) sulfide has been oxidized to lead(II) sulfate.
The oxidation state of sulfur increased from -2 in lead(II) sulfide to +6 in lead(II) sulfate.
3. PbO (s) + H2 (g) -> Pb (s) + H2O (g)
Lead(II) oxide has been reduced to lead.
The oxidation state of lead decreased from +2 in lead(II) oxide to 0 in lead.
4. 2FeCl2 (aq) + Cl2 (g) -> 2FeCl3 (aq)
FeCl2 has been oxidized to FeCl3.
The oxidation state of iron increased from +2 in iron(II) chloride to +3 in iron(III) chloride.