Ozone composition

Question 1

what are the main gases of the ozone?

Answer 1

Nitrogen = 78%
Oxygen = 21%
Argon = 1%
Carbon Dioxide = 350 ppm

Question 2

what happens to the atmosphere the higher you go?

Answer 2

the atmosphere becomes less dense

Question 3

what are the two sections of the atmosphere below 50km called?

Answer 3

up to 15km = troposphere
15-50km = stratosphere

Question 4

whats in the troposphere

Answer 4

90% of all molecules in the atmosphere are there

Question 5

what are the two equations for the formation of the ozone?

Answer 5

O2 + hv => 2O
O + O2 => O3

Question 6

what are the two equations for the break down of the ozone?

Answer 6

O3 + hv => O2 + O (sunscreen effect)
O + O3 => 2O2 (catalysed by radicals)

Question 7

how do halogen radicals remove O3?

Answer 7

Halogen radicals act as a catalyst, removing O3 from the atmosphere by providing an alternative route with a lower Ea.

Question 8

which other radicals can catalyse the destruction of the ozone?

Answer 8

NO
OH
Br

Question 9

what’s the general equation for the destruction of the ozone (X=catalyst)

Answer 9

1. X + O3 => XO + O2
2. XO + O => X + O2
   overall: O3 + O => 2O2

Question 10

why is accelerated destruction of the ozone undesirable?

Answer 10

because the ozone absorbs harmful high energy UV. if this energy is not absorbed it can cause problems such as skin cancer, damaged DNA, eye damage, damage to crops

Question 11

why is ozone in the troposphere undesirable?

Answer 11

produced by emissions from cars (NO), it is undesirable since it is both:
- toxic to humans
- causes photochemical smog

Question 12

where do halogen radicals come from?

Answer 12

small amount from the breakdown of CH3Cl and CH3Br (given off from oceans, burning vegetation)
majority from the break down of ChloroFluoroCarbon CFC’s were used widely for refrigerants, cleaning products and propellants for aerosols.
CFCs are unreactive in the troposphere, but in the stratosphere the high energy UV causes photodissociation so the C-Cl bond breaks (homolytic dissociation)

Question 13

describe where particulates come from and their polluting effects

Answer 13

source: volcanoes, burning fuels, burning coal
polluting effects: penetrate deep into the human body causing heart attacks and lung cancer

Question 14

describe where VOC (volatile organic compounds) comes from and its polluting effects

Answer 14

source: plants, unburnt fuel from engines
polluting effects: photochemical smog

Question 15

describe where CO (carbon monoxide) comes from and its polluting effects

Answer 15

sources: burning biomass, incomplete combustion of hydrocarbons in fossil fuels
polluting effects: toxic gas, photochemical smog

Question 16

describe where CO2 (carbon dioxide) comes from and its polluting effects

Answer 16

source: combustion of fossil fuels
polluting effects: greenhouse effect

Question 17

describe where NOx (nitrogen oxides) comes from and its polluting effects

Answer 17

source: combustions of fuels in power stations and vehicles
polluting effects: photochemical smog, acid rain

Question 18

describe where SOx (sulphur oxides) comes from and its polluting effects

Answer 18

source: volcanoes, burning of fuels containing sulphur
polluting effects: toxic gas, acid rain

Question 19

why is oxygen not usually converted to ozone in the troposphere?

Answer 19

the UV levels are too low, they aren’t a high enough frequency to break the bonds