Answer:
1. Reduction: O₂ ; Oxidation: S
2. Reduction: F ; Oxidation: Al
3. Reduction: Zn ; Oxidation: H
Explanation:
Determine the oxidation state of each element:
2 CoS → Cobalt acts with +2, S with -2
O₂ is at ground state. In ground state the elements has oxidation state of 0.
In CoO, the oxygen acts with -2
The oxidation state has decreased; oxygen was reduced.
In SO₂, sulfur acts with +4; oxidation state has increased, so S has been oxidized.
2. Both reactants are at ground state.
In AlF₃ Al has oxidation state of +3 and F, -1
Al increased the oxidation state → oxidation
F decreased the oxidation state → reduction
3. Hydrogen has 0 as oxidation state. In water, H has +1
It was increased → oxidation
Zn acts with +2, in the zinc oxide. As we have elemental Zn, the oxidation state is 0; it has decreased → reduction
