Chemistry Reference
In-Depth Information
brown acidic gas nitrogen(
iv
) oxide (nitrogen
dioxide).
nitrogen monoxide + oxygen → nitrogen(
iv
)
oxide
2NO(
g
) + O
2
(
g
) → 2NO
2
(
g
)
This dissolves in water to produce nitric acid (this is
a contributor to acid rain; see Chapter 12 p. 198).
Many non-metal oxides, such as nitrogen dioxide
and carbon dioxide (see Chapter 13 p. 214), form
acidic solutions.
Concern about pollution due to cars has led to the
introduction of strict regulations and now all new cars
must have a device known as a catalytic converter fitted
to eliminate the production of some of these gases.
The catalytic converter acts as a device to speed
up reactions which involve the pollutant gases,
converting them to less harmful products, such as
nitrogen and carbon dioxide. It should be noted that
catalytic converters can only be used with unleaded
petrol as the lead 'poisons' the catalyst, preventing it
from catalysing the reactions. For a further discussion
of catalytic converters see Chapter 7, p. 110.
Figure 11.23
Particulates produced by diesel engines are a real health
problem worldwide.
have been associated with a variety of lung complaints
in both adults and children.)
Heavy industry (Figure 11.24) and power stations
are major sources of sulfur dioxide, formed by the
combustion of coal, oil and gas, which contain small
amounts of sulfur.
sulfur
Another method that has been introduced to
reduce the amount of pollutants is that of the 'lean
burn' engine. Although this type of engine reduces
the amounts of carbon monoxide and oxides of
nitrogen produced, it actually increases the amount
of hydrocarbons in the exhaust gases.
A further method of regulating pollutant gases is
to convert petrol-burning engines to LPG (liquid
petroleum gas) engines, whilst retaining the ability to
burn petrol. These cars are known as dual-fuel cars.
Much research is directed towards an efficient electric
motor that can be fitted in place of the petrol engine in
a car. This development is moving forward at a pace.
+ oxygen →
sulfur dioxide
S(
s
)
+
O
2
(
g
) →
SO
2
(
g
)
Internationally, the use of lead compounds as
additives remains an issue because of the continued
use of leaded petrol. However, the concern about
these additives is lessening as worldwide recognition
of the problems of lead pollution in the environment
and its effects on living systems is leading to their
being removed from petrol. Perhaps of greater
concern globally will be the increase of
particulates
in the air (Figure 11.23). ('Particulates' is a general
term used to describe very small particles in the
atmosphere, such as certain types of smoke emitted
from diesel engines, as well as dust. These particulates
Figure 11.24
Sulfur dioxide is a major pollutant produced by industry.
