Final answer:
The redox processes among the options given are a) NO₂ → NO₃⁻, b) Cr³⁺ → CrO₄²⁻, and d) SO₃ → SO₄²⁻, which involve oxidation, while e) VO₃ → VO₂ involves reduction. Option c) is not a recognized chemical transformation and may be incorrect.
Step-by-step explanation:
To determine whether the processes a) NO₂ → NO₃⁻, b) Cr³⁺ → CrO₄²⁻, c) CO₂ → CO₃²⁻, d) SO₃ → SO₄²⁻, and e) VO₃ → VO₂ are redox processes, we would need to analyze the oxidation states of the elements involved before and after the transformation. A redox process implies a change in the oxidation states reflecting a transfer of electrons between substances.
- a) NO₂ → NO₃⁻: The oxidation state of nitrogen increases; thus, this is an oxidation process.
- b) Cr³⁺ → CrO₄²⁻: Here, chromium goes from a +3 to a +6 oxidation state, meaning it is being oxidized.
- c) CO₂ → CO₃²⁻: This process does not actually occur as CO₂ does not spontaneously convert to CO₃²⁻; this appears to be a typo or error.
- d) SO₃ → SO₄²⁻: Sulfur's oxidation state increases from +4 to +6, indicating oxidation.
- e) VO₃ → VO₂: In this process, vanadium is reduced since its oxidation state decreases from +5 to +4.
These changes in oxidation states indicate that options a), b), and d) represent redox processes specifically involving oxidation, while option e) involves reduction. Option c) seems to be an error as it's not a common or viable chemical transformation.
Charge balance is crucial in redox reactions to uphold the principle of conservation of charge. Changes in oxidation state must be compensated by the transfer of electrons so the overall charge remains constant before and after the reaction.