Sulfur dioxide is the main gas responsible for reducing smog. It reduces other gases in the atmosphere while also oxidizing to sulfur trioxide, which dissolves in water to form an acidic mist or smog. There are two ways this can happen - through heterolytic catalysts like unburnt hydrocarbons that weaken bonds, or through free radical catalysts produced when nitrogen dioxide molecules split due to UV light. Both catalysts can help sulfur dioxide and other gases convert to sulfur trioxide and ultimately sulfuric acid smog.

1. SMOG

2. Reactions in reducing Smog The gas mainly responsible is sulfur dioxide. It is called a reducing smog because the sulfur dioxide reduces other gases in the atmosphere producing a range of other pollutants. At the same time the sulfur dioxide is oxidized to sulfur trioxide which dissolves in water to produce a mist or smog.

3. Reducing Smog This can happen in 2 ways: Heterolytic catalyst. Free radical catalysts.

4. Heterolytic catalyst. Unburnt hydrocarbons or metal ions in the air are called particulates Oxygen atoms can absorb these particulates, weakening the bond and catalyzing their reaction with SO2 into SO3 .

5. SO2(g) + O2(g) ---- SO3(g)

6. It then reacts with water in the atmosphere to form acidic smog SO3(g) + H2O(l) H2SO4(aq)

7. The free radicals is produced by the fission of a nitrogen dioxide molecule in the presence of UV light Which in turns produce oxygen free radicals. NO2(g) --NO(g) + O*(g) Free radical catalysts.

8. These highly reactive oxygen atoms can react directly with SO2. SO2(g) +O* --- SO3(g)

9. This free radical will then catalyze the reaction of either sulfur dioxide or nitrogen oxides Giving off sulfuric or nitric acid mist/smog