Option E Environmental Chemistry
Primary Air Pollution
El.
E2
E.l
HL/SL
For each of the primary pollutants below, state one chemical method used to reduce the amount
entering the atmosphere and give one relevant equation relating to the chemistry behind the method.
(a)
Carbon monoxide, CO: .......................................................................................................
[2]
(b)
Nitrogen(II) oxide, NO: .........................................................................................................
[2]
(c)
Sulfur(IV) oxide, SO 2 : ...........................................................................................................
[2]
(d)
Gasoline (petrol), C8Hl8:
[2]
....................................................................................................
Particulates are a type of primary air pollutant produced in several industries and by the burning of
fuels.
(a) The emission of particulates by some industries is reduced by an electrostatic method.
Explain how this is done.
[3]
(b)
State one type of fuel that is very likely to produce particulates when burned.
[1]
(c)
Deduce the equation for a combustion reaction of methane in which particulates are formed.
[1]
E3.(a)
CO, NO, SO 2 and hydrocarbons are primary air pollutants.
(i)
(ii)
(b)
(c)
The levels of CO and NO produced by automobiles can be lowered by a catalytic
converter. Write a balanced chemical equation for the reaction that takes place between
these two primary pollutants in a catalytic converter.
[2]
SO 2 is produced from the burning of coal. It can be removed from the exhaust gases
of coal-burning power plants by alkaline scrubbing. Write a balanced chemical
equation for the reaction that takes place in the scrubber.
[2]
Write chemical equations to show the formation of acid rain from one of the primary
pollutants above.
State one adverse health effect of
hydrocarbons.
[2]
[1]
Option E Environmental Chemistry
Ozone
1.
(a)
E.2
HL/SL
The presence of small amounts of ozone in the upper atmosphere is necessary for human health.
Write equations (two in each case) to show the natural formation and depletion of ozone in
the upper atmosphere.
ozone formation
[4]
........................................................................................................................
ozone depletion ............................................................................................................................
(b)
CFCs are substances that have caused a decrease in atmospheric ozone concentration hi
recent years.
(i)
State what the letters CFC stand for and list two sources of CFCs in the atmosphere.
[3]
(ii)
Outline two harmful effects on human health due to the decrease in atmospheric ozone.
[2]
(iii)
Discuss two disadvantages of using C 4 H 10 as an alternative to CFCs.
[2]
Ozone Depletion
2.
HL ONLY
Ozone depletion in the upper atmosphere poses a threat to living organisms.
(a)
Describe, with the help of balanced equations, the ozone-oxygen system that existed in the
upper atmosphere before its disturbance by human activities. In your answer describe the
role of light in this process and discuss the importance of wavelength in the reactions
involved.
(b) Discuss the role of chlorofluorocarbons (CFCs) in the process of ozone depletion. Your
answer should include a description of the mechanism and an explanation as to why a small
amount of CFCs has such a large effect on the ozone layer.
[5]
[5]
E3
The natural concentration of ozone in the upper atmosphere is kept unchanged by a sequence of
reactions, including the following:
The bonding in the ozone molecule can be represented as two resonance hybrids, one of which is
shown below.
(a)
Draw a Lewis structure for the oxygen molecule.
[1]
(b) By reference to the bonding in ozone and oxygen, state and explain whether the wavelength
and energy of the radiation required for reaction II would be less than or greater than that
required for reaction I.
[3]
Turn over
E.3
Option E Environmental Chemistry
Greenhouse Gases and Acid Rain
E1.
HL/SL
The term greenhouse effect is used to describe a natural process for keeping the average temperature
of the Earth's surface nearly constant.
(a)
(b)
Describe the greenhouse effect in terms of radiations of different wavelengths.
Water vapour acts as a greenhouse gas. State the main natural and man-made sources of water
vapour in the atmosphere.
[4]
[2]
Natural source .......................................................................................................................
Man-made source .............................................................................................................. ...
(c)
Two students disagreed about whether carbon dioxide or methane was more important as a
greenhouse gas.
(i)
State one reason why carbon dioxide could be considered more important than methane
as a greenhouse gas.
[1]
(ii) State one reason why methane could be considered more important than carbon dioxide
as a greenhouse gas.
(d)
Discuss the effects of global warming on the Earth.
[1]
[4]
E2. (a) Explain using an equation why rain falling in unpolluted air is acidic with a pH of about 5.7.
(b) "Acid rain" has a pH less than 5.6. Explain using an equation how the burning of coal can
contribute to acid rain formation.
(c)
(d)
[2]
[2]
"Acid rain" can affect plants and buildings.
(i)
Outline how an acidic soil can damage the growth of trees.
[1]
(ii)
Give an equation for the reaction of acid rain on marble statues or limestone buildings. [1]
Explain how the addition of calcium oxide to lakes could neutralize the effects of "acid rain". [1]
(e) (i)
Identify the two major pollutants that cause acid rain. For each, state the man-made source.
[4]
(ii) For each of the pollutants mentioned in (b) (i), outline two different methods by which
their contribution to acid rain could be reduced.
[4]
Smog
HL ONLY
3 , The oxides of nitrogen in vehicle exhaust emissions can contribute to photochemical smog.
(a) Discuss the atmospheric and land features that favour the formation of photochemical smog
in large cities.
(b)
(c)
[4]
Ozone is a secondary pollutant present in photochemical smog. It is formed by free radical
mechanisms. State what is meant by the term free radical, and use equations to explain how
ozone is formed from nitrogen(II) oxide, NO.
[4]
State one type of secondary pollutant formed from hydrocarbons in photochemical smog and
outline one harmful effect of the pollutant.
[2]
E4 . Photochemical smog is an increasing problem. Outline the causes and effects of photochemical
smog by referring to each of the following:
•
•
•
•
its origin
the weather conditions needed
the chemical compounds present
the effects on human health.
[6]
E4
Option E Environmental Chemistry
Water Treatment
El.
SL/HL
Nitrates in drinking water can cause health problems.
(a) Identify one source of nitrates in drinking water and explain why nitrates can be a health
problem.
[2]
(b) Identify the stage of waste water treatment in which nitrates can be removed and state one
method for nitrate removal.
[2]
(c)
Many impurities in waste water are removed by secondary treatment.
Describe how this is done.
E2. (a)
State what is meant by the term biological oxygen demand (BOD).
[4]
[2]
(b)
Organic matter in water can be decomposed by both aerobic and anaerobic bacteria.
(i)
State which type of bacteria is more likely to be active in water with a low BOD value.
[1]
(ii)
The following elements can occur in organic matter. Suggest one gas that is likely to be
produced from each element when organic matter is decomposed by anaerobic bacteria
[3]
carbon
nitrogen
sulfur
3.
(a)
(b)
4.
Two processes used to treat sewage are filtration and chemical precipitation.
(i)
Name the type of substance removed by filtration and the equipment used to do this.
[2]
(i)
Name the type of substance removed by chemical precipitation and a chemical used to
do this.
[2]
(i) State two advantages of treating drinking water with ozone rather than chlorine.
[2]
(ii) Other than cost, name one disadvantage of treating drinking water with ozone rather
than chlorine.
[1]
Explain why water is such a good solvent for many substances. State two reasons why the supply
of fresh water is inadequate to meet global demands. Explain the principles behind the use of both
reverse osmosis and ion exchange to obtain fresh water from sea water.
[10]
Toxic Substances in Water
HL ONLY
E5. Compounds of heavy metals are one type of toxic substance found in water. Outline one source in water
supplies and one effect, different in each case, on human health, for each of the metals mercury and lead.
mercury
lead
(b)
Lead and nitrates represent a health hazard in polluted water. Identify a source of each of these
pollutants, state a health hazard caused by each pollutant, and indicate a way by which the
concentration of each can be reduced.
E6. (a)
(b)
(c)
Discuss the disadvantages of the different ways of expressing toxicity. Your answer should
include the definitions of the terms LD50 and maximum daily tolerance.
[6]
The maximum safe limit for nitrates in drinking water has been set at 50 mg dm-3 by the
World Health Organization. Calculate the maximum mass of sodium nitrate permissible in
one litre (1.00 dm3) of drinking water assuming no other source of nitrate is present.
[2]
Nitrates are thought to pose a risk to very small babies as they can lead to oxygen starvation.
State why nitrates are also toxic to adults.
[2]
Option E Environmental Chemistry
\a
(a)
E4
Water pollution and Treatment
Explain what is meant by Biological Oxygen Demand (BOD) and describe the effect of a
high BOD in water.
[2]
MOO
(b)
(c)
Identify the stage of sewage treatment which removes the substances responsible for BOD
and explain how this is done.
[S]
Discuss how the addition of nitrates or phosphates to water can contribute to the BOD.
[2]
N02/420/H(3)
9
Many impurities in waste water are removed by secondary treatment. Describe how this is
done.
[4]
MO 1/42(VH(3)
3.
(a)
Two processes used to treat sewage are filtration and chemical precipitation.
(i)
(ii)
(b)
(i)
(ii)
Name the type of substance removed by filtration and the equipment used to do this.
[2]
Name the type of substance removed by chemical precipitation and a chemical used to
do this.
f2J
State two advantages of treating drinking water with ozone rather than chlorine.
[2]
Other than cost, name one disadvantage of treating drinking water with ozone rather
than chlorine.
I*J
N01/420/H(3)
/4-, Explain why water is such a good solvent for many substances. State two reasons why the supply
of fresh water is inadequate to meet global demands. Explain the principles behind the use of both
reverse osmosis and ion exchange to obtain fresh water from sea water.
[10]
Toxic Substances in Water
HL ONLY
N01/42O/H(3)
5
Three different types of pollutants which can be found in water are heavy metals, pesticides
and PCBs.
(a)
(b)
(c)
What do the letters PCB stand for?
[1]
The toxicity of pesticides can be expressed either as an LD 50 value or as a maximum daily
tolerance value.
(i)
State what is meant by both LD50 value and maximum daily tolerance value.
[2]
(ii)
State one advantage and one disadvantage associated with either of the two values.
[2]
Mercury is a heavy metal which is toxic to humans.
(i)
State one common source of mercury in polluted water.
[1]
(ii)
State one symptom shown by humans who are suffering from mercury poisoning.
[1]
(iii) Explain why mercury is poisonous to
humans.
[1]
(o. (a)
(i)
(ii)
Explain the meaning of the term LD S0 .
State one advantage and one disadvantage of the use of LDS0 .
(b) Lead and nitrates represent a health hazard in polluted water. Identify a source of each of
these pollutants, state a health hazard caused by each pollutant, and indicate a way by which
the concentration of each can be reduced.
[2]
[2]
[6]