atmospheric chemistry Flashcards
1
Q
oxygen (the reactive gas)
A
- most reactive gas in air
- prep in lab by decomposition of hydrogen peroxide (H₂O₂)
- manufactured in industry by liquefaction followed by fractional distillation of air
- air turned into liquid + diff gases allowed to boil at diff temps
2
Q
nitrogen (the unreactive gas)
A
- -most abundant gas in air (78%)
- colourless, odourless, tasteless gas
- so unreactive bc of large amount of energy required to break triple bond between N atoms
- essential for plant growth (need to make proteins)
- so unreactive it cannot be used directly by plants
3
Q
nitrogen fixation
A
conversion of atmospheric nitrogen to useful compounds
4
Q
two methods of nitrogen fixation
A
- during thunderstorms/lightning
- nitrogen-fixing bacteria
5
Q
during thunderstorms
A
- discharge of electricity that takes place during thunderstorms provides enough energy for nitrogen + oxygen in air to react together.
- substance called nitrogen monoxide, NO, formed
- ntrogen monoxide reacts w/ oxygen from air to form nitrogen dioxide
- nitrogen dioxide dissolves in rainwater to form nitrous acid, HNO₃
6
Q
nitrogen-fixing bacteria
A
- plants called legumes (eg. peas, beans) have tiny root swellings containing rhizobium bacteria which can fix nitrogen
- not enough nitrogen fixed by natural processes to provide for out needs
- soils for growing crops must have fertiliser added
- fertiliser produced by artificial fixation (eg. Haber process)
7
Q
nitrogen recycling
A
- nitrogen must be recycled throughout an ecosystem + returned to atmosphere
- bacteria called nitrifying + denitrifying bacteria necessary in process of recyling
- nitrogen cycle
8
Q
inorganic carbon compounds
A
- carbon dioxide,
- carbon monoxide (CO),
- carbonate compounds,
- hydrogencarbonate compounds,
- carbides
9
Q
carbon burned in limited supply of oxygen
A
- if carbon burned in limited supply of oxygen, carbon monoxide formed instead of carbon diozide
eg. in car engines, in cigarette smoke
10
Q
the carbon cycle
A
- percentage of carbon dioxide in atmosphere fairly constant at 0.03%
- some processes remove CO₂ from air, others return it to air
11
Q
processes that remove CO₂ from air
A
-photosynthesis
6CO₂ + 6H₂O –> C₆H₁₂O₆ + 6O₂
-dissolving in rainwater, rivers, oceans, some of the CO₂ becomes incorporated into limestone
12
Q
processes that return CO₂ to the air
A
- respiration by living things
- burning of fossil fuels
- roasting of limestone
13
Q
the green house effect
A
Greenhouse gases: CO₂, water vapour
-greenhouse effect keeps the earth warm enough to live on
14
Q
greenhouse factor
A
measure of the greenhouse effect (heat-absorbing properties) of a particular gas when compared with carbon dioxide
15
Q
what gases are not greenhouse gases?
A
nitrogen
oxygen
16
Q
increase in greenhouse gases - carbon diozide
A
- human activities leading to inc in conc of greenhouse gases in air
- level of CO₂ giving cause for concern. Burning of of fossil fuels results in large amounts of CO₂ being added to air
- inc in rate at which CO₂ released into air not matched by rate at which it is removed by photosynthesis or by dissolving in oceans etc
- residence time of CO₂in air about 100 years
17
Q
greenhouse gases
A
methane
CFCs (chlorofluorocarbons)
dinitrogen oxide N₂O
18
Q
methane - activity that is increasing its concentration
A
- increasing size of cattle herds - animals release large amount of methane from intestines
- growing of rice in paddy fields
- anaerobic breakdown of organic material in rubbish dumps
19
Q
methane - residence time
A
10 years
20
Q
CFCs (chlorofluorocarbons) - activity that is increasing its concentration
A
- propellant gas in aerosol sprays
- discarded fridges
21
Q
CFCs (chlorofluorocarbons) - residence time
A
100 years
22
Q
dinitrogen oxide N₂O - activity that is increasing its concentration
A
car exhaust fumes
23
Q
dinitrogen oxide N₂O - residence time
A
100 years
24
Q
enhanced greenhouse effect
A
- increasing concentrations of greenhouse gases in atmosphere may be leading to an “enhanced” greenhouse effect
- may bring about an increase in temp on surface of planet, referred to as global warming
25
potential implications of global warming
climate change
| rise in sea level
26
climate change
-more extreme weather conditions will develop eg. severe storms, drought in some areas, flooding
27
rise in sea level
- extra heat may lead to melting of polar ice caps
- add to climate change + causes rise in sea level
- greatest increase in volume of water in sea will be as direct result of extra heat
- will lead to water in oceans expanding, leading to flooding of low-lying areas of planet
28
benefits of enhanced greenhouse effect
-increase in rate of photosynthesis in plants
| would come about due to increase in carbon dioxide levels in air
29
strategies for bringing reversal of increase in CO₂
- developing alternative energy sources other than fossil fuels
- growing many more trees worldwide
30
atmospheric pollution
air pollution
| acid rain
31
air pollution
occurs when there is too much of a certain substance so that it may cause a significant hazard to present or future health or to the environment
32
acid rain
- rainwater naturally acidic due to presence of Carbonic acid (H₂CO₃) - from dissolved CO₂) pH 5.2
- acid rain is acidic rain caused by pollytion from SO₂ and NO₂
33
SO₂
- SO₂ present in air
- SO₂ reacts w/ oxygen in air to form sulfur trioxide SO₃
- sulfur trioxide then dissolves in rainwater to form sulfuric acid
34
NO₂
- oxides of nitrogen lead to acid rain
- prod by burning fossil fuels in power stations +high temps created by spark plugs in car engines. high temperature provides enough energy to cause nitrogen gas to combine w/ oxygen gas
- nitrogen monoxide combines w/ oxygen in air to form nitrogen dioxide
- nitrogen dioxide dissolves in water to form mixture of nitrous acid + nitric acid
35
harmful effects of acid rain
- damage to trees
- leaching of metal ions eg. aluminium, out of soil into lakes (can interfere with gill mechanism of fish, killing them)
- buildings + statues made of limestone eroded by acid rain
36
scrubbing systems
use of scrubbing systems in chimneys of power stations decreased incidence of acid rain caused by sulfur dioxide
37
calcium sulfite
SO₂ is made to combine w/ limestone to form calcium sulfite CaSO₃
limestone + sulfur dioxide --> cakcium sulfite + carbon dioxide
CaCO₃ + SO₂ --> CaSO₃ + CO₂
38
the ozone layer
- Trioxygen, O₃, a form of oxygen more commonly known as ozone.
- There is a layer of ozone surrounding Earth about 25 km above Earth's surface
39
where the ozone layer is formed
- formed in stratosphere by reaction between an oxygen radical + an oxygen molecule
- oxygen radicals formed when ultraviolet light of particularly high energy breaks oxygen molecule into oxygen atoms
40
the ozone layer - oxygen radicals
- 2 oxygen radicals formed
- as soon as oxygen radicals formed, they react w/ the oxygen molecules in atmosphere to form ozone
- when ozone formed absorbs ultraviolet, photodissociation of ozone occurs. Ie. above reaction is reversed + ozone is decomposed
- some of oxygen radicals produced destroy ozone molecules by converting them to oxygen molecules
- oxygen molecules broken down by UV light to form oxygen radicals which lead to production of ozone
41
screening effect of ozone
reaction 2 responsible for the very important screening effect of ozone since it absorbs much of the harmful ultraviolet radiation
42
excessive exposure to UV light
causes skin cancer
43
ozone layer - oxygen radical - reaction 1
O* + O₂ --> O₃ (formation of ozone)
44
ozone layer - oxygen radical - reaction 2
O₃ --> O₂ + O*
45
ozone layer - oxygen radical - reaction 3
O* + O₃ --> 2O₂
46
CFCs
Chlorofluorocarbons are compounds of chlorine, fluorine, and carbon
47
CFCs characteristics
- low boiling points
- low toxicity
- low flammability
- v. unreactive
48
properties that CFCs use were based on
- propellant gases in aerosol sprays
- foaming agent in making expanded polystyrene
- as a cooling agent in fridges + air-conditioning systems
49
CFCs and the ozone
- lack of reactivity has lead to CFCs being responsible for depletion of zone in stratosphere
- can travel unchanged as far as the stratosphere. Ther, they are broken down by high level of ultraviolet radiation present
eg. CC₃F --> CCl₂F* + Cl*
50
CFC
| reaction (i)
chlorine atoms then attack ozone to form oxygen + chlorine oxide
O₃ + Cl* --> O₂ + ClO*
51
CFC
| reaction (ii)
Chlorine oxide v. reactive (it is a radical) + attacks an oxygen atom
ClO* + O* --> Cl* + O₂
52
CFCs cycle
Reaction (ii) releases more chlorine atoms to attack ozone molecules as in reaction (i). Thus, cycle continues + chain reaction occurs
Chlorine atom used up in (i) regenerated in reaction (ii). Every time (i) occurs, ozone molecule destroyed. Estimated that one Cl atom can destroy tens of thousands of molecules of ozone
53
methane benefit
helps to prevent damage to ozone layer despite causing problems as a greenhouse gas
54
Methane and Cl
methane reacts w/ Cl radicals + prevents concentration of chlorine radicals building up. Helps to slow down rate at which ozone is being destroyed
CH₄ + Cl* --> *CH₃ + HCl
55
CFCs substitutes
replacement compounds are called hydrochlorofluorocarbons (HCFCs) since they contain hydrogen, chlorine, fluorine + carbon
56
HCFCs
- Presence of the C-H bonds means molecules broken down by radicals naturally present in lower atmosphere (troposphere). Hence, do not reach ozone in stratosphere
- Do destroy some ozone since they contain some chlorine but destroy a lot less than CFCs do
- research taking place to develop CFC + HCFC substitutes w/o chlorine in their molecules.
- ->Such compounds are called hydrofluorocarbons, HFCs. These are hydrogen-containing fluoroalkanes, eg. CH₂FCF₃
57
uses of oxygen
- in hospitals for people w/ difficulty breathing
- in purification of river water
- in welding + cutting
58
uses of nitrogen
- manufacture of ammonia
- keep food fresh by preventing oxidation (due to unreactiveness) eg. crisps
- remove skin cancer (warts, verrucae)
- freezing food/biological specimens
59
liquid nitrogen (-196°C)
- quick-freezing of food
| - remove warts
60
other way ozone can be formed
electric discharge that takes place during lightning storms + in photocopiers + electric motors
61
concentration of ozone
expected to remain constant as due to reactions 1-3, ozone is being made + destroyed continuously
62
atoms mainly responsible for destroying ozone
- chlorine
| - substances called chlorofluorocarbons responsible for producing chlorine atoms in atmosphere + causing much of damage
63
NO₂ equations
hardback
64
how nitrogen oxides produced
produced by burning fossil fuels in power stations + at high temp created at the spark plug in car engines
65
SO₂ equations
hardback
66
How SO₂ present in air
- present due to volcanic activity + rotting vegetation
- result of burning fossil fuels. These fuels contain small amount of sulfur. When fuel burned, sulfur combines w/ oxygen to form sulfur dioxide
67
nitric acid
- falls to earth in rainwater + forms nitrate (NO₃-) compounds in soil
- absorbed by plants through roots + become incorporated into plant's tissues in form of proteins
68
nitrogen fixing - thunderstorms
| equations
N₂ + O₂ --> 2NO
N₂ + 2O₂ --> 2NO₂
2NO₂ + H₂O --> HNO₂ + HNO₃
69
respiration by living things
C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O
70
nitrogen cycle
pic in hardback
71
uses of carbon dioxide
- carbon dioxide used to put "fizz" in drinks, used in ire extinguishers, + in form "dry ice" which is used to refrigerate items being transported
- solid carbon dioxide used to create "mist" effect on stage
72
powdered carbon
-powdered carbon can be burned in air producing carbon dioxide C + O₂ --> CO₂
73
how carbon dioxide released
- carbon dioxide released when acid added to calcium carbonate
- produced during process called fermentation
74
carbon monoxide
- colourless gas with no smell
- highly poisonous
- does not dissolve in water
- doe snot react with acids or bases
- a neutral oxide
75
chemical equations
know the chemical equations
76
which gas makes the greatest contribution to the greenhouse effect? and why?
water vapour
| -it is the most plentiful/highest concentration
77
balanced equations on how sulfuric acid in rainwater is formed from sulfur dioxide in the atmosphere
SO₂ + 1/2O₂ --> SO₃
SO₃ + H₂O --> H₂SO₄
78
beneficial effect of the ozone layer
absorbs ultraviolet radiation
79
How is ozone formed in the stratosphere?
-Ultraviolet radiation breaks oxygen (O₂) molecules into separate atoms (radicals)
O₂ --> 2O*
-these oxygen atoms react with oxygen molecules (O₂) to form ozone (O₃)
O* + O₂ --> O₃
80
describe using balanced equations why chlorine radicals are so damaging to the ozone layer
Cl* + O₃ --> ClO* + O₂
ClO* + O* --> Cl* + O₂
81
why are HCFCs less damaging to the ozone layer than CFCs?
- broken down before they reach stratosphere
- shorter atmospheric residence times
- more reactive than CFCs
- less stable than CFCs
82
Define "greenhouse gases"
-gases that absorb heat/energy/infra-red radiation in the atmosphere
/
-gases that retain (prevent escape of) heat/energy/infra-red radiation into outer atmosphere
83
state one global climate change implication of failure to control greenhouse gas emissions
- global warming
- melting of polar ice-caps
- rise in sea levels
- wildlife endangered
84
describe how chlorofluorocarbons are broken down in the stratosphere
-broken down by ultraviolet radiation
85
two ways to reduce emissions of greenhouse gases
- ban use of CFCs
- use CFC substitutes
- plant more trees + avoid deforestation
- use renewable power
- reduce fossil fuel dependency
86
why is rainwater always acidic even when there is no air pollution?
due to dissolved carbon dioxide (CO₂)
87
two damaging effects of 'acid rain' on the environment
- damange to plants
- fish kills
- corrosion
- damage to limestone buildings + monuments
88
show, by means of equations, how sulfur dioxide pollution in the atmosphere results in 'acid rain'
SO₂ + H₂O --> H₂SO₃
SO₂ + 1/2 O₂ --> SO₃
SO₃ + H₂O --> H₂SO₄
89
how does human activity contribute to increasing sulfur dioxide levels in the atmosphere?
- burning fossil fuels
| - waste incineration
90
Why Ireland's air quality is of a high standard
- small population
- little heavy industry
- windy
- burning smoky fuels in cities forbidden
- prevailing wind from Atlantic
91
balanced equation for formation of ozone in stratosphere
O₂ -(UV)-> 2O*
O* + O₂ --> O₃
92
why is nitrogen gas chemically intert (incl all reasons)
- high energy bond
- non-polar
- triple bond
93
Describe how atmospheric nitrogen gas is fixed by lightning
- lightning supplies the high temp req for N₂ to combust
- nitrogen combines with oxygen to produce nitrogen(II) oxide
- NO combines with oxygen to give nitrogen dioxide
- NO₂ combines with moisture (H₂O) to give nitrite
94
chemical processes that give rise to the occurrence of ozone gas in stratosphere
- decomposition of oxygen into oxygen atoms (Radicals) by ultraviolet light
- reaction of oxygen atom (radical) with oxygen molecule forming ozone
95
why is ozone gas not produced in the lower atmosphere?
- lack of ultra-violet light
| - oxygen not decomposed
96
why do CFC molecules have long residence times in the lower atmosphere?
- stable
- insufficient ultraviolet light
- insoluble in water
97
uses of CFCs
- refrigerant (fridges)
- aerosols
- air-conditioning
- dry cleaning
- solvents
- fire extinguishers
98
name the non-metallic oxide that is associated with ozone destruction in the stratosphere + give a source of this oxide
-nitrogen(II) oxide
sources:
- electrical discharge
- car engines
- exhaust gases
- micro-organisms
99
balanced equation for the photodissociation of ozone
O₃ --> O₂ + O*
100
effects of damage to ozone layer
- sunburn (skin damage)
- eye damage
- damage to plants
- skin cancer (melanoma, skin disease)
101
examples of CFCs
CCl₂F₂
102
acidic oxide
oxide that increases hydrogen ion (H+) concentration in water
/ oxide that neutralises base(s)
103
human activities that contribute to to addition of carbon dioxide to atmosphere
- respiration
- combustion
- deforestation
- landfill
- aerosols
104
chemical species that form as a result of carbon dioxide gas dissolving in water
- carbonate ion
- hydrogencarbonate ion
- carbonic acid
- hydronium ion
- hydrogen ion
105
reagent used in scrubbers to remove acidic oxides
- limestone
- lime
- sodium carbonate
- magnesia
106
list some greenhouse gases
- water
- methane
- CFCs
- HFCs
- chloromethane
- chloroethane
107
describe how an increase in the no. of cars has contributed to an increase of NO₂
-spark plug/high temp/compression in ignition system provides energy for first reaction
N₂ + O₂ --> 2NO
2NO + O₂ --> 2NO₂
108
chemical equation for chain reaction process whereby chlorine free radicals break down ozone in the stratosphere
Cl* + O₃ --> ClO* + O₂
ClO* + O* --> O₂ + Cl*
109
gases in the atmosphere which contribute to the greenhouse effect
- carbon dioxide
- methane
- CFC
- water
110
Gases in the atmosphere that are not greenhouse gases
- nitrogen (N₂)
| - oxygen (O₂)
111
How CFCs give rise to ozone depletion
- release chlroine free radicals
- radicals attack ozone
- reaction with oxygen free radicals, chain reaction
- releasing chlorine free radicals again
