To determine what is being oxidized in the reaction:
[tex]\[\text{CO}_2(g) + \text{H}_2(g) \longrightarrow \text{CO}(g) + \text{H}_2\text{O}(l)\][/tex]
we need to analyze the changes in oxidation states of the elements involved in the reaction.
1. Oxidation State of Carbon in CO₂ (carbon dioxide):
- In CO₂, each oxygen has an oxidation state of -2.
- Since there are two oxygens, the total oxidation state contributed by oxygen is \(2 \times -2 = -4\).
- To balance this, the oxidation state of carbon must be +4.
- Thus, the oxidation state of carbon in CO₂ is +4.
2. Oxidation State of Hydrogen in H₂ (molecular hydrogen):
- In its elemental form, hydrogen has an oxidation state of 0.
- Thus, the oxidation state of hydrogen in H₂ is 0.
3. Oxidation State of Carbon in CO (carbon monoxide):
- In CO, oxygen has an oxidation state of -2.
- To balance this, the oxidation state of carbon must be +2.
- Thus, the oxidation state of carbon in CO is +2.
4. Oxidation State of Hydrogen in H₂O (water):
- In H₂O, oxygen has an oxidation state of -2.
- There are two hydrogens, each usually having an oxidation state of +1.
- Thus, the oxidation state of each hydrogen in H₂O is +1.
Now, we compare the changes in oxidation states from the reactants to the products:
- Carbon:
- It goes from +4 in CO₂ to +2 in CO.
- A decrease in oxidation state means that carbon is being reduced, not oxidized.
- Hydrogen:
- It goes from 0 in H₂ to +1 in H₂O.
- An increase in oxidation state means that hydrogen is being oxidized.
Hence, the element whose oxidation state increases is hydrogen. Therefore, the substance being oxidized in this reaction is hydrogen.
