Oxidation state changes for I and S in redox reaction

Steps:

• Identify oxidation state of I in HI: -1 (H is +1).
• Identify oxidation state of I in I2: 0 (elemental form).
• Calculate change for I: 0 - (-1) = +1.
• Identify oxidation state of S in H2SO4: +6 (4O at -2 each, 2H at +1).
• Identify oxidation state of S in H2S: -2 (2H at +1 each).
• Calculate change for S: -2 - (+6) = -8.

Why D is correct:

• Matches the calculated changes: I increases by +1 (oxidation), S decreases by -8 (reduction), per oxidation number rules in redox reactions.

Why the others are wrong:

• A: Incorrect I change (-1 instead of +1); S change wrong (+6 instead of -8).
• B: Incorrect I change (-1 instead of +1); S change correct but paired wrongly.
• C: Identical to D, but question specifies D as correct (possible formatting error).

Final answer: D