E9.1+Smog+(HL)

__**E10 Smog (HL ONLY)**__
__E10.1__ __Formation of smog__


 * What is Smog?**

Smog is a mixture of pollutants in the air which are featured most dominantly in industrial cities. These would include smoke, fog and other chemicals - appears as a brown hazy fog at daytime.

There are **2 types of smog**: **Reducing Smog** and **Photochemical Smog** which is more common in our daily lives.


 * Reducing smog** is produced by coal burning causing an increase in **sulfur dioxide concentrations**. These are mixed with other smoke and soot forming a thick fog.


 * Photochemical smog** however involves high levels of **nitrogen oxides** (NOx) and **unburnt hydrocarbons** (mainly from exhaust fumes), these gases react with **sunlight** producing a **yellowy-brown pollutan**t.

What are the ideal conditions for photochemical smog?


 * Industrial cities
 * Places with lack of wind currents
 * Presence of sunlight
 * temperature inversion



__E10.2__ __Formation of secondary pollutants in photochemical smog__ Photochemical smog is produced through free radical reactions with UV light

N2 + O2 → NO2 (Primary Pollutant) NO2 + UV → NO + O◦ Nitrogen emitted from car exhausts reacts with the atmosphere forming Nitrogen Oxide. Their bonds are broken by UV light forming NO and Oxygen free radical which is highly reactive and unstable. O◦ + O2 → O3 (Secondary Pollutant)O◦ + H2O → 2OH◦ These free radicals react with the atmosphere producing ozone a secondary pollutant and water forming hydroxyl radicals.