The part
carbon dioxide plays in environmental processes
Carbon dioxide is one of the most abundant gasses in the atmosphere. Carbon dioxide plays an important part in vital plant and animal process, such as photosynthesis and respiration. These processes will be briefly explained here.Green plants convert carbon dioxide and water into food compounds, such as glucose, and oxygen. This process is called photosynthesis.
The reaction of photosynthesis is as follows:
6 CO2 + 6 H2O --> C6H12O6 + 6 O2
Plants and animals, in turn, convert the food compounds by combining it with oxygen to release energy for growth and other life activities. This is the respiration process, the reverse of photosynthesis.
The respiration reaction is as follows:
C6H12O6 + 6 O2 --> 6 CO2 + 6 H2O
Photosynthesis and respiration play an important role in the carbon cycle and are at equilibrium with one another.Photosynthesis dominates during the warmer part of the year and respiration dominates during the colder part of the year. However, both processes occur the entire year. Overall, then, carbon dioxide in the atmosphere decreases during the growing season and increases during the rest of the year.Because the seasons in the northern and southern hemispheres are opposite, carbon dioxide in the atmosphere is increasing in the north while decreasing in the south, and vice versa. The cycle is more clearly present in the northern hemisphere; because it has relatively more land mass and terrestrial vegetation. Oceans dominate the southern hemisphere.
Influence of carbon dioxide on alkalinity
Carbon dioxide can change the pH of water. This is how it works:
Carbon dioxide dissolves slightly in water to form a weak acid called carbonic acid,
H2CO3 , according to the following reaction:
CO2 + H2O --> H2CO3
After that, carbonic acid reacts slightly and reversibly in water to form a hydronium cation, H3O+, and the bicarbonate ion, HCO3-, according to the following reaction:
H2CO3 + H2O --> HCO3- + H3O
This chemical behaviour explains why water, which normally has a neutral pH of 7 has an acidic pH of approximately 5.5 when it has been exposed to air.
