Pollution: Earning Utcomes
Pollution: Earning Utcomes
Pollution: Earning Utcomes
Pollution
LEARNING OUTCOMES
Define the term environment;
Solution
Chapter 26
Pollution
Solution to Quick check 1
1. (a) Oxygen is obtained from the industry by the fractional distillation of liquid air.
(b) (i) Oxygen is used in oxy-acetylene flames for cutting metal.
(ii) Oxygen is used by deep-sea divers and mountaineers.
2. (a) 2C2H2 + 5O2 4CO2 + 2H2O
(b) If there is an insufficient supply of oxygen, combustion will be
incomplete and carbon monoxide and soot will be formed.
3. (a) Combustion is an exothermic reaction between a substance
and oxygen with or without flames. Burning is combustion
accompanied by the presence of flames.
(b) Respiration is a process by which oxygen is taken in by
living things to oxidise food into carbon dioxide, water and energy.
Photosynthesis is a process by which green plants take in
carbon dioxide and water with the help of sunlight to make
carbohydrates, releasing oxygen in the process.
Return
Chapter 26
Pollution
Air Pollution
The air we breathe in may not be clean. It
may be polluted by substances called
pollutants.
Return
Chapter 26
Pollution
Acid rain
Acid rain has a pH of
between 1–5 compared to
normal rain water which
has a pH of about 5.6.
Acid rain is rain that contains
a large proportion of acids
such as sulphuric acid and
nitric acid.
When sulphur dioxide in the air reacts with oxygen and water, it forms sulphuric acid:
2SO2 + O2 + 2H2O 2H2SO4
Nitrogen dioxide in the air reacts with oxygen and water to form nitric acid:
4NO2 + O2 + 2H2O 4HNO3
These two acids dissolve in the rain water to form acid rain.
Chapter 26
Pollution
Harmful effects of acid rain
Acid rain corrodes buildings, bridges, statues and other
structures made of metal or stone.
Acid rain kills fishes in lakes and rivers.
Acid rain kills plants and vegetation by damaging their
roots, leading to deforestation in many parts of the world,
like Canada and Europe.
Chapter 26
Pollution
Prevention of acid rain
Use fuels with less sulphur content, e.g. natural gas instead of coal.
Treat acidic waste gases from factories and power stations with calcium oxide
or calcium carbonate before releasing them into the air.
Use catalytic converters in motor vehicles to reduce emissions of nitrogen
oxides.
2. (a) State the gases which cause acid rain and describe how these
acids are formed by the named gases.
(b) State two harmful effects of acid rain.
(c) State two ways of reducing acid rain.
Solution
Chapter 26
Pollution
Solution to Quick check 3
1. (a) carbon monoxide: Prevent forest fires, install catalytic converters in motorcars;
(b) nitrogen oxides: treat waste gases from factories and power stations with calcium
oxide, install catalytic converters in motorcars;
(c) sulphur dioxide: use natural gas instead of coal in power stations, treat waste
gases from factories and power stations with calcium oxide;
(d) unburned hydrocarbons: install catalytic converters in motorcars.
2. (a) Acid rain is caused by the presence of sulphuric and nitric acids in the rain.
Sulphuric acid and nitric acid are formed when sulphur dioxide and nitrogen
dioxide react with oxygen and water in the atmosphere respectively as follows:
2SO2 + O2 + 2H2O 2H2SO4
4NO2 + O2 + 2H2O 4HNO3
(b) Acid rain destroys stone buildings and statues, kills plants and causes
deforestation. Return
(c) Acid rain can be reduced by removing sulphur dioxide and nitrogen oxides from
waste gases by treating them with calcium oxide. Avoid the burning of coal and
fuel oil that contains large amounts of sulphur.