Page 201 - Chemistry ICSE Class IX
P. 201
Atmospheric Pollution 189
What are the Harmful Effects of Carbon Monoxide
When fossil fuels are burnt in a limited quantity of air (oxygen), the products
of combustion are CO (carbon monoxide) and H O.
2
For example, when coal is burnt in limited quantity of air, carbon
monoxide is produced.
2C(s) + O (g) o 2CO(g)
2
in coal Oxygen in air Carbon monoxide
(limited quantity)
Carbon monoxide is highly poisonous. It has 200 times more
af nity for haemoglobin than oxygen. When inhaled, carbon monoxide
combines with haemoglobin in the blood to form carboxyhaemoglobin.
Carboxyhaemoglobin cannot carry oxygen. This causes a de ciency of
oxygen in the heart and brain tissues resulting in suffocation and even
death.
Hb + CO(g) o CO . Hb
haemoglobin Carboxyhaemoglobin
How can the carbon monoxide pollution be controlled
Carbon monoxide pollution can be controlled by the following actions:
By replacing the automobiles tted with internal combustion engine
by electrically powered automobiles.
The internal combustion engines should be modi ed to allow complete
combustion of petrol/diesel. Complete combustion of petrol/diesel
will produce only CO and H O vapour. Many automobiles are tted
2
2
with such engine systems.
By using cleaner fuels, such as compressed natural gas (CNG) or
liquid natural gas (LNG) or ethanol (alcohol) blended petrol.
By using an automobile tted with catalytic converter. Catalytic
converter uses platinum catalyst and work in two stages to eliminate
the harmful pollutants from the exhaust gases.
The catalyst platinum (Pt) gets poisoned by heavy metal e.g., lead
(present in petrol as tetraethyl lead). To prevent the poisoning of Pt catalyst,
lead-free petrol should be used.
Smog
The smoke + fog conditions are called smog.
There are two types of smog:
Chemical smog
Photochemical smog
What is the chemical smog Smog
The chemical smog occurs in cold, humid climate due to the built up of
sulphur dioxide (SO ) and smoke particulates. Sulphur dioxide in the
2
presence of moisture form droplets of sulphurous acid (H SO ).
3
2
