Oxidation Number Changes in Redox Reactions

Steps:

• Assign oxidation number to C in CO: +2 (since O is -2).
• Assign oxidation number to C in CO₂: +4 (two O atoms total -4).
• Calculate change for C: +4 - (+2) = +2 (oxidation).
• Assign oxidation number to N in NO: +2 (O is -2); in N₂: 0 (elemental form).
• Calculate change for N: 0 - (+2) = -2 (reduction).

Why D is correct:

• D states carbon +2 and nitrogen -2, matching the exact increases/decreases per oxidation number rules for redox species.

Why the others are wrong:

• A: Reverses both signs; carbon decreases, nitrogen increases—opposite of oxidation/reduction.
• B: Carbon change is +2, not +1; nitrogen -2, not -1.
• C: Carbon increases (+2), not decreases (-1); nitrogen decreases (-2), not increases (+1).

Final answer: D