Chemistry Reference
In-Depth Information
Questions
1
Write word and balanced chemical equations to show the
effect of heat on cobalt carbonate (CoCO
3
) and nickel
carbonate (NiCO
3
).
2
Write word and balanced chemical equations for the
reaction of dilute hydrochloric acid with:
a
copper(
ii
) carbonate
glucose + oxygen → carbon dioxide + water + energy
C
6
H
12
O
6
(
aq
) + 6O
2
(
g
) → 6CO
2
(
g
) + 6H
2
O(
l
)
Carbon dioxide is taken in by plants through their
leaves and used together with water, taken in
through their roots, to synthesise sugars. This is the
process of
photosynthesis
, and it takes place only
in sunlight and only in green leaves, as they contain
chlorophyll
(the green pigment) which catalyses
the process.
b
sodium carbonate.
●
Carbon dioxide
Carbon forms two oxides - carbon monoxide (CO)
and carbon dioxide (CO
2
). Carbon dioxide is the
more important of the two, and in industry large
amounts of carbon dioxide are obtained from the
liquefaction of air. Air contains approximately 0.03%
by volume of carbon dioxide. This value has remained
almost constant for a long period of time and is
maintained via the
carbon cycle
(Figure 13.13).
However, scientists have recently detected an increase
in the amount of carbon dioxide in the atmosphere
to approximately 0.04%.
sunlight
carbon dioxide + water
glucose
+ oxygen
chlorophyll
6CO
2
(
g
)
+ 6H
2
O(
l
)
C
6
H
12
O
6
(
aq
) + 6O
2
(
g
)
The carbon cycle has continued in this manner for
millions of years. However, scientists have detected
an imbalance in the carbon cycle due to the increase
in the amount of carbon dioxide produced through
burning fossil fuels and the deforestation of large
areas of tropical rain forest. The Earth's climate is
affected by the levels of carbon dioxide (and water
vapour) in the atmosphere. If the amount of carbon
dioxide, in particular, builds up in the air, it is
thought that the average temperature of the Earth
will rise. This effect is known as the
greenhouse
effect
(Figure 13.14).
Some energy from the Sun is absorbed by
the Earth and its atmosphere. The remainder
is refl ected back into space. The energy that is
absorbed helps to heat up the Earth. The Earth
radiates some heat energy back into space but
the 'greenhouse gases', including carbon dioxide,
prevent it from escaping. This effect is similar
to that observed in a greenhouse where sunlight
(visible/ultraviolet radiation) enters through
the glass panes but heat (infrared radiation) has
diffi culty escaping through the glass. Other gases
also contribute to the greenhouse effect. One
of these is methane, which is produced from
agriculture and released from landfi ll sites as well as
rice fi elds.
The long-term effect of the higher temperatures
of the greenhouse effect and the subsequent
global
warming
will be the continued gradual melting of
ice caps and consequent fl ooding in low-lying areas
of the Earth. There will also be further changes in the
weather patterns which will further affect agriculture
worldwide.
carbon dioxide
in the air
SUN
photosynthesis
respiration
animals take in oxygen,
eat plants and breathe
out CO
2
plants give out oxygen
burned as fue
ls
producing
CO
2
death and decay
decay
carbon compounds
in oil, gas, coal
and carbonates
Figure 13.13
The carbon cycle.
Carbon dioxide is produced by burning fossil fuels.
It is also produced by all living organisms through
aerobic respiration
. Animals take in oxygen and
breathe out carbon dioxide.
