Atmospheric Chemistry

Question 1

how far is the atmosphere

Answer 1

extends about 100km

Question 2

how far is thin air

Answer 2

6 km up the air is too thin to breath

Question 3

what does the atmosphere consist of

Answer 3

mixture of gases
similar all over the earth due to mixing
1. caused by rotation of earth
2. heating of earth by sun

Question 4

composition of earth

Answer 4

nitrogen 
oxygen
carbon dioxide 
noble gases
water 
pollutants

Question 5

production of oxygen

Answer 5

1. natural production
   made by green plants using photosynthesis
   6CO2 + 6H2O = C6H12O6 + 6O2
2. industrial production
   fractional distillation of liquid air
   a) scrub air - remove water and dust
   b) liquefy - compressing then cooling then releasing
   c) separate - let liquid warm up gases will boil of when their boiling point is reached

Question 6

boiling points

Answer 6

Bigger atoms (molecules) have higher boiling points due to bigger attraction between molecules caused by Van der Waal’s Forces

0C = K - 273
K = oC + 273
[ -273 0C = Absolute Zero]

Question 7

uses of oxygen

Answer 7

1. oxygen in hospitals
2. cellular respiration
3. combustion
4. steel making
5. in rockets

Question 8

nitrogen

Answer 8

unreactive
needs lots of energy to break n triple bond n

lightning can provide this forming NO2
N2 + 2O2 = 2NO2

NO2 dissolves in rain to form nitrites and nitrates
H2O + 2NO2 = HNO2 + HNO3

HNO2 = nitrites
HNO3 = nitrates

Question 9

uses of nitrogen

Answer 9

1. Haber process - making ammonia
2. liquid nitrogen to freeze pizzas
3. filling crisp packets - prevent crushing

Question 10

nitrogen cycle

Answer 10

atmospheric nitrogen 78 %
nitrification 
denitrifying bacteria 
nitrates in soil 
death and decay 
absorbed by plants
plants 
death and decay
animals 
eaten as food
death and decay and excretion

Question 11

noble gases

Answer 11

He - filing airships
Ar - filing light bulbs
Ne - neon light

Question 12

inorganic carbon compound

Answer 12

co produced by incomplete combustion
co is a neutral oxide
no effect on universal indicator

Question 13

types of oxide

Answer 13

Acidic
neutral
basic

Question 14

types of oxide

Answer 14

Acidic
neutral
basic

Question 15

CO2
PRODUCED
USED

Answer 15

produced - respiration, burning, rotting, fermentation
used in - photosynthesis, fire extinguishers, fizzy drinks

carbon dioxide is an acidic oxide
CO2 + H2O -> H2CO3
carbonic acid is a weak acid - it turns Universal Indicator yellow

Question 16

carbon cycle

Answer 16

atmospheric CO2 0.03%
plants 
photosynthesis 
animals 
eaten 
respiration 
respiration 
solution 
oceans
death and decay 
fossil fuels 
carbonate rocks
roasting limestone

Question 17

greenhouse gases

Answer 17

CO2
CH4
CFCs
H2O

levels of CO2 are getting too high
due to increase in use of fossil fuels, rainforest burning, deforestation
CH4 from oil fields, rubbish dumps and cattle belching

more violent weather
rising sea levels

Question 18

pollution

Answer 18

Addition of any damaging substance to the environment

Question 19

atmospheric pollution example

Acid rain formation and effect

Answer 19

SULPHUR DIOXIDE S02
from- volcanoes 
fossil fuel combustion 
industry 
S + O2 = SO2

Acid rain has a pH of less than 4.5
SO2 dissolves in rainwater to form H2SO3 [sulphurous acid]
SO2(g) + H2O(l) = H2SO3(aq)

Sulphurous acid then reacts with O2 in air
H2SO3(aq) + ½ O2(g) = H2SO4(aq)
[sulphuric acid]

causes

1. corrosion
2. health effects
3. death of animals
4. death of plants

Question 20

Nitrogen Dioxide NO2

Answer 20

N2 generally unreactive

N2(g) + O2(g) = 2 NO(g)
[nitrogen monoxide - colourless gas]
NO(g) + 1/2 O2(g) = NO2(g)
[nitrogen dioxide - brown gas]
2 NO2(g) + H2O(l) = HNO2(aq) + HNO3(aq)

Nitrous acid Nitric acid

Question 21

Other Pollutants

Answer 21

Lead and lead compounds (Pb)
Replaced by Volatile Organic Chemicals [VOC’s] e.g. benzene
VOC + O2 + UV => O3 (poisonous)

Question 22

CFCs

HCFCs

Answer 22

If we change a Cl in CCl4 for a F then we get CFCl3 a ChloroFluoroCarbon a CFC

HCFCs = HydroChloroFluoroCarbons

Question 23

ozone layer

Answer 23

O3
formed in stratosphere
25 - 50 km up
Absorbs harmful UV radiation from sun
UV burns and causes cancer.

Question 24

Formation of Ozone

Answer 24

O2 = (UV) O radical + O radical
oxygen splitting called photodissociation {breaking of a bond using light}

O radical + O2 = O3
Most of the oxygen radicals [atoms] formed in this way react with oxygen molecules to form ozone again.
In this way even more harmful UV is absorbed and ozone is not depleted

some ozone lost due to oxygen radicals react with ozone form oxygen
O radical + O3 = 2O2

Question 25

CFC’s

Answer 25

Chlorine radicals are produced by CFCs (ChloroFluoroCarbons)
Contain Chlorine, Fluorine and Carbon
Used as aerosol propellants, fire extinguishers
residence time of 100 years

Question 26

CFCs and UV

Answer 26

CCl3F => UV CCL2F radical + CL radical
O3 + CL radical => O2 + CLO radical
CLO radical + O radical => Cl radical + O2

One Cl atom can destroy tens of thousands of O3 (by a chain reaction)

Question 27

Other Ozone Destroyers

Answer 27

Nitrogen monoxide [NO]

O3 + NO = O2 + NO2

Question 28

Helpers

Answer 28

Methane (CH4) a serious greenhouse gas helps use up chlorine atoms

Cl radical + CH4 => CH3 radical + HCL
Gets rid of chlorine atoms [radicals]