Let's analyze each reaction in turn to determine whether it is an oxidation-reduction reaction, characterized by changes in oxidation states of the elements involved.
### Reaction 1:
[tex]\[ ZnS (s) + 2 O_2 (g) \rightarrow ZnSO_4 (s) \][/tex]
- Zinc (Zn):
- In ZnS, zinc has an oxidation state of +2.
- In ZnSO_4, zinc also has an oxidation state of +2.
- Sulfur (S):
- In ZnS, sulfur has an oxidation state of -2.
- In ZnSO_4, sulfur has an oxidation state of +6.
- Oxygen (O):
- In O2 (g), oxygen has an oxidation state of 0.
- In ZnSO_4, oxygen has an oxidation state of -2.
In this reaction:
- Zinc does not change its oxidation state.
- Sulfur changes from -2 to +6 (oxidation).
- Oxygen changes from 0 to -2 (reduction).
Since there are changes in oxidation states, this reaction is indeed an oxidation-reduction (redox) reaction.
### Reaction 2:
[tex]\[ CaO (s) + H_2O (l) \rightarrow Ca(OH)_2 (s) \][/tex]
- Calcium (Ca):
- In CaO, calcium has an oxidation state of +2.
- In Ca(OH)_2, calcium maintains an oxidation state of +2.
- Oxygen (O):
- In CaO, oxygen has an oxidation state of -2.
- In H2O, oxygen has an oxidation state of -2.
- In Ca(OH)_2, oxygen maintains an oxidation state of -2.
- Hydrogen (H):
- In H2O, hydrogen has an oxidation state of +1.
- In Ca(OH)_2, hydrogen maintains an oxidation state of +1.
Since there are no changes in oxidation states, this is not a redox reaction.
### Reaction 3:
[tex]\[ 6 Li_2O (s) + P_4O_{10} (g) \rightarrow 4 Li_3PO_4 (s) \][/tex]
- Lithium (Li):
- In Li_2O, lithium has an oxidation state of +1.
- In Li_3PO_4, lithium still has an oxidation state of +1.
- Phosphorus (P):
- In P4O10, phosphorus has an oxidation state of +5.
- In Li_3PO_4, phosphorus maintains an oxidation state of +5.
- Oxygen (O):
- In Li_2O, oxygen has an oxidation state of -2.
- In P_4O_{10}, oxygen has an oxidation state of -2.
- In Li_3PO_4, oxygen maintains an oxidation state of -2.
Since there are no changes in oxidation states, this is not a redox reaction.
### Reaction 4:
[tex]\[ SO_2 (g) + H_2O (l) \rightarrow H_2SO_3 (aq) \][/tex]
- Sulfur (S):
- In SO_2, sulfur has an oxidation state of +4.
- In H_2SO_3, sulfur still has an oxidation state of +4.
- Oxygen (O):
- In SO_2, oxygen has an oxidation state of -2.
- In H_2O, oxygen has an oxidation state of -2.
- In H_2SO_3, oxygen maintains an oxidation state of -2.
- Hydrogen (H):
- In H_2O, hydrogen has an oxidation state of +1.
- In H_2SO_3, hydrogen does not change its oxidation state of +1.
Since there are no changes in oxidation states, this is not a redox reaction.
Based on the analysis above, only Reaction 1:
[tex]\[ ZnS (s) + 2 O_2 (g) \rightarrow ZnSO_4 (s) \][/tex]
is an oxidation-reduction (redox) reaction.
