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Atmospheric Chemistry Flashcards

(88 cards)

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1
Q

what is the atmosphere?

A

a layer of gases

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2
Q

atmospheric composition: nitrogen

A

78%

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3
Q

atmospheric composition: oxygen

A

21%

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4
Q

how does oxygen exist

A

as oxygen gas O2

and ozone O3

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5
Q

manufacture of oxygen 2

A

extracted from the atmosphere by;

  • liquifying the air
  • fractionally distilling the air
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6
Q

manufacture of oxygen

first step

A

air is filtered to remove dust particles

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7
Q

manufacture of oxygen

how is carbon dioxide removed?

A

air is passed through sodium hydroxide to remove CO2

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8
Q

manufacture of oxygen

how is water removed?

A

water vapour condenses out during compression and in drying towers using silica gel

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9
Q

manufacture of oxygen

what occurs during compression

A

the air heats up

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10
Q

manufacture of oxygen

how to cool air

A

the air is passed through a heat exchanger where it is cooled by cold nitrogen in a fractioning column

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11
Q

manufacture of oxygen

in fractioning tower

A

liquified air is distilled, oxygen collects at he bottom and nitrogen at the top

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12
Q

manufacture of oxygen

why is oxygen further purified

A

purified to remove inert gases such as neon and krypton

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13
Q

4 uses of oxygen

A

steelmaking
welding
medicine
recreational

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14
Q

steelmaking - use of oxygen

A

to remove carbon, silicon and phosphorous from cast iron as there oxides

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15
Q

welding - use of oxygen

A

when ethyne is burned in oxygen temperatures of about 3000ºC are reached

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16
Q

how is nitrogen found?

A

as N2

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17
Q

is nitrogen gas reactive or unreactive?

A

chemically unreactive due to the high bond energy of the triple bond between its atoms

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18
Q

why is nitrogen important

A

as it is a constituent of protein that is essential for muscle cells and blood cells

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19
Q

Natural Fixation of Nitrogen

A

any process that produces useful compounds from atmospheric nitrogen

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20
Q

3 natural fixation of nitrogen methods

A

lightning
bacteria
decomposition

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21
Q

how does lightning naturally fixate nitrogen?

A

at very high temperatures nitrogen and oxygen combine to form nitrogen monoxide, then combines with atmospheric oxygen to form nitrogen dioxide - dissolves in rain water to give nitrous and nitric acids, HNO2 and HNO3. fall on earth and deposited in soil, make plant protein

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22
Q

how does bacteria naturally fixate nitrogen?

A

certain species are capable of fixing atmospheric nitrogen into nitrates that plants can absorb to make plant proteins.
some are free in soil - Azotobacter, some in plants eg. clover and sweet pea - Rhizobium

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23
Q

how does decomposition naturally fixate nitrogen?

A

most of the nitrates in soil come from dead and decaying plants and animals

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24
Q

an example of an artificial fertiliser

A

ammonium nitrate

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25
4 uses of nitrogen
freezing food packaging of food reduce the flammability of chemicals manufacture of ammonia and nitric acid
26
how does nitrogen help with freezing food?
liquid nitrogen is used to fast freeze foods which is less damaging to food than normal freezing
27
how does nitrogen help with packaging food?
crisps are packed in nitrogen as it prevents oxidation of the oils
28
how does nitrogen reduce the flammability of chemicals?
nitrogen is used to reduce the oxygen content in storage tanks, thus reducing the flammability of certain chemicals it is also used to flush out dangerous vapours in tanks
29
manufacture of ammonia
nitrogen is used as feedstock in the manufacture of ammonia
30
equation for how lightning naturally fixates nitrogen
N2 + O2 -> 2NO
31
heat change of how lightning naturally fixates nitrogen
endothermic
32
shape of CO2
linear
33
Combustion of carbon dioxide eqn.
C + O2 -> CO2
34
carbon dioxide as an acid in water
CO2 + H2O -> H2CO3
35
H2CO3
carbonic acid (weak)
36
what does aqueous carbon dioxide form?
an equilibrium mixture containing hydrogen ions, carbonate ions and hydrogen carbonate ions
37
2 equations for equilibrium mixture containing hydrogen ions, carbonate ions and hydrogen carbonate ions
H2CO3 ⇌ H+ + HCO3- | H2CO3 ⇌ 2H+ + CO3 2-
38
can carbonic acid be isolated as a single substance ?
no
39
4 uses of carbon dioxide
carbonated drinks fire extinguishers cooling agent (dry ice) in the manufacture of urea
40
what type of fire would you put out with carbon dioxide?
electrical
41
when is carbon monoxide formed?
if carbon is burned in a limited supply of oxygen
42
formation of carbon monoxide eqn.
C + 1/2 O2 -> CO
43
what type of oxide is carbon monoxide
neutral oxide - does not react with water
44
why is CO poisonous
it deprives the body of oxygen
45
where is CO present?
in cigarette smoke and car exhaust fumes
46
fermentation of glucose equation
C6H12O6 -> 2C2H5OH + 2CO2
47
enzyme for fermentation of glucose
zymase
48
greenhouse gasses
gases in the atmosphere that absorb infra-red radiation from the sun
49
examples of greenhouse gases
``` carbon dioxide methane water vapour nitrous oxide ozone CFCs ```
50
how much of the atmosphere is CO2
0.035%
51
most abundant greenhouse gas
CO2
52
what accounts for the increase in CO2
burning of fossil fuels and deforestation
53
what reduces CO2
absorbed by oceans
54
what accounts for more water vapour
global warming
55
what can help to block sun rays
in increase of water in clouds
56
concentration of methane in atmosphere
1.7 ppm
57
why is there an increase in methane
``` waste from homes cattle populations swamps, bogs and paddy fields aerobic fermentation trapped in ice - melting ```
58
how effective is methane
20 times more effective than CO2
59
how effective are CFCs
40 times more effective than CO2
60
problem with CFCs
the breakdown of CFCs in the atmosphere release chlorine radicals that break up the ozone layer
61
what is the ozone layer responsible for?
for protecting the earth from uv radiation
62
residence time of CO2
50 to 200 years
63
residence time of methane
10 years
64
residence time of CFCs
50 to 100 years
65
4 possible implications of the increased greenhouse effect
rise in sea levels extinction of some plants increase in levels of CO2 and methane disruption to agriculture
66
3 sources of air pollution
domestic industrial vehicles
67
describe domestic pollution
fuels contain sulfur and carbon and when burned from sulfur dioxide and carbon dioxide. SO2 dissolves in water to produce acid rain, which kills vegetation and damages buildings, increased CO3 cause an increase in global temperature. smoke and dust particles are produced which cause smog which blackens buildings and can cause respiratory problems
68
describe industrial pollution
the fuels used in industry e.g. oil and natural gase, release sulfur dioxide and carbon dioxide
69
describe vehicle pollution
exhaust fumes produce unburned hydrocarbons, carbon monoxide and the oxides of nitrogen and lead nitrogen monoxide and nitrogen dioxide cause acid rain and respiratory problems. Leas and its compounds are toxic and affect the brain. (catalytic converters)
70
when is acid rain caused
when gases such as carbon dioxide, nitrogen dioxide and sulfur dioxide dissolve in water to form carbonic acid (H2CO3), nitrous acid (HNO2) and sulfurous acid (H2SO3)
71
effects of acid rain on the environment
``` corrosion of buildings reduction of crop yield extinction of some plants leaching of heavy metals from soil reduction of fish numbers when snow melts into water ```
72
3 preventative measures against acid rain
reduction in use of fossil fuels use of catalytic converters scrubbing of waste gases using limestone to remove pollutants from waste gases
73
ozone
triatomic form of oxygen, O3
74
describe ozone
a pale blue gas that is pleasant at low concentrations but is toxic at high concentrations and damages plant life
75
significance of ozone layer
ozone protects life on earth from ultra-violet radiation
76
formation of ozone
ultra-violet radiation breaks up oxygen molecules into oxygen free radicals, they then combine with molecules of oxygen to form ozone
77
formation of ozone eqn.
O2 -> 2O• | O• + O2 -> O3
78
photodissociation of ozone
destroyed by uv light | constantly being formed and broken up, usually at a steady rate
79
photodissociation of ozone eqn.
O3 -> O2 + O•
80
uses of CFCs
solvents in dry-cleaning refrigerators and air conditioning - coolants aerosols
81
stratosphere
upper atmsophere
82
eqn. for breakdown of CFCs in the stratosphere
n
83
removal of ozone
reactive chlorine atoms break up ozone to form oxygen and chlorine monoxide, that reacts when oxygen to form chlorine
84
equation for removal of ozone
Cl• + O3 -> ClO + O2 | ClO + O• -> Cl• + O2
85
i single chlorine atom
can destroy 1 million ozone molecules
86
oxygen atoms destroying ozone eqn.
O• + O3 -> 2O2
87
nitrogen monoxide destroying ozone
NO + O3 -> NO2 + O2
88
eqn. for methane absorbing chlorine
CH4 + 2Cl -> CH3Cl + HCl

Chemistry (Tara) (50 decks)

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