Catalyst and reagent in SO₂ acid rain formation

Steps:

• Step 1 oxidizes SO₂ to SO₃ via atmospheric catalysis.
• NO₂ acts as catalyst: SO₂ + NO₂ → SO₃ + NO.
• Step 2 forms H₂SO₄ by SO₃ reacting with water.
• Option C matches: NO₂ (catalyst), H₂O (reagent).

Why C is correct:

• NO₂ catalyzes oxidation (SO₂ + NO₂ → SO₃ + NO), and H₂O hydrolyzes SO₃ (SO₃ + H₂O → H₂SO₄) per acid rain chemistry.

Why the others are wrong:

• A: O₂ directly oxidizes SO₂ too slowly without catalyst; not atmospheric role for step 1.
• B: NO₂ correct for step 1, but O₂ does not react with SO₃ to form H₂SO₄.
• D: Identical to B; wrong reagent for step 2.

Final answer: C