Photochemical Smog

Question 1

major constituents in the atmosphere

Answer 1

N2, 78%; O2, 20%

Question 2

properties of nitrogen

Answer 2

exists as a diatomic molecule (N2) held by covalent triple bonds (super strong), and takes large amounts of energy to break the triple bond and form new compounds.

Question 3

formation of oxides of nitrogen (NOx)

Answer 3

with sufficient energy from high temps:
N2 + O2 –> 2NO (nitric oxide)
2NO + O2 –> 2NO2 (nitrogen dioxide)

Question 4

what is the troposphere?

Answer 4

the lowest layer of the atmosphere containing 75% of all gases by mass in the atmosphere.

Question 5

atmosphere levels

Answer 5

lowest to highest: troposphere, stratosphere, mesosphere, thermosphere, exosphere

Question 6

pollutants in photochemical smog

Answer 6

NO, NO2, CO3, UHC
nitric oxide, nitric dioxide, ozone, unburned hydrocarbons

Question 7

formation of ozone

Answer 7

N2 + O2 –> 2NO
2NO + O2 –> 2NO2
NO2 -(UV)-> NO + O
O + O2 –> O3

Question 8

what is photochemical smog?

Answer 8

a complex mixture of primary chemicals (directly from a source) and secondary chemicals (from reactions involving light and heat) between pollutants in the atmosphere.

Question 9

conditions of photochemical smog

Answer 9

1. high concentration of pollutants (in urban areas the conc can vary throughout the day)
2. sunlight (UV to photodissociate NO)
3. still air mass (heat can disperse)
4. temperature inversion (warmer air becomes trapped in cooler air)

Question 10

what is temperature inversion?

Answer 10

when warm air is trapped between layers of cooler air, the pollutants are trapped in the first cool layer.