Final answer:
When nitrogen dioxide (NO₂) converts to dinitrogen tetroxide (N₂O₄) upon cooling, there is no change in oxidation state for nitrogen. Therefore, the process involves neither oxidation nor reduction.
Step-by-step explanation:
Nitrogen dioxide (NO₂) converts to dinitrogen tetroxide (N₂O₄) when cooled. This chemical reaction involves two NO₂ molecules combining to form one N₂O₄ molecule. When considering the concepts of oxidation and reduction in the context of this reaction:
- Oxidation involves the loss of electrons or an increase in oxidation state by a molecule, atom, or ion.
- Reduction involves the gain of electrons or a decrease in oxidation state by a molecule, atom, or ion.
In the reversible reaction 2 NO₂(g) ⇌ N₂O₄(g), there is no change in oxidation state for nitrogen; it remains the same in both NO₂ and N₂O₄. Since there is no transfer of electrons and no change in oxidation states of the nitrogen, neither oxidation nor reduction is occurring during the formation of dinitrogen tetroxide from nitrogen dioxide upon cooling.