Ocean pH

Coccoliths are very small shells of calcium carbonate that form around a number of species of algae. Algae play an important role in the global carbon-oxygen cycle and thus in our ecosystem. Scientists at the Nano-Science Center, University of Copenhagen, have measured how individual coccoliths react to water with different degrees of acidity.

Coccoliths which have a mass of about 500 pg (0.0000000005 g), were weighed before and after they had been immersed in water with different acidities. The results enable the scientists to say something about how important the water acidity is for the marine environment.

The world's oceans are acidifying due to our emissions of carbon dioxide. Over time the pH of the Earth's oceans is decreasing:

Time	pH
18th century	8.179
Recent past (1990s)	8.104
Present levels	~8.069
2050 (estimated)	7.949
2100 (estimated)	7.824

Coccoliths are protected from dissolution by a very thin layer of organic material that the algae form, even though the seawater is extremely unsaturated relative to calcite (calcium carbonate). The protection of the organic material is lost when the pH is lowered slightly. In fact, it turns out that the shell falls completely apart when experiments are done in water with a pH value of 7.8, the pH that many researchers believe will be the found in the world oceans in the year 2100.

Reference:
T. Hassenkam, A. Johnsson, K. Bechgaard, S. L. S. Stipp. Tracking single coccolith dissolution with picogram resolution and implications for CO2 sequestration and ocean acidification. Proceedings of the National Academy of Sciences, 2011; DOI: 10.1073/pnas.1009447108\

Further Reading:
Carbon Cycle
Combustion of Hydrocarbons
Acid Rain
Mass Conversions
pH Calculations
Acid Dissociation Constants (Ka)

Study Questions:

1. Write the formula for:
   
   • carbon dioxide
   • calcium carbonate
2. Calculate the percentage composition of
   
   • carbon dioxide
   • calcium carbonate
3. Write a balanced chemical equation to show the production of carbon dioxide from the combustion of methane (a fossil fuel).
4. Assuming 100 tonnes of methane gas were combusted under standard laboratory conditions:
   
   • What is the maximum mass of carbon dioxide that could be produced?
   • What volume would this mass of carbon dioxide occupy?
5. Coccoliths have a mass of about 500 pg. Convert this to a mass in:
   • milligrams
   • micrograms
   • nanograms
   • kilograms
6. The current pH of ocean water is approximately 8.069. Assuming the temperature of the oceans to be 25^oC, calculate the current:
   • hydrogen ion concentration of ocean water
   • hydroxide ion concentration of ocean water
   • pOH of ocean water
   
   
7. In 2100, the pH of ocean water is predicted to be 7.824. Assuming the temperature of the oceans to be 25^oC, calculate the:
   • hydrogen ion concentration of ocean water in 2100
   • the hydroxide ion concentration of ocean water in 2100
   • the pOH of ocean water in 2100
   • the increase in hydrogen ion concentration between now and 2100
     
   
   
   
8. For the reaction: H₂CO₃ HCO₃^- + H⁺ K_a = 4.5 x 10^-7
   
   • Is H₂CO₃ a strong acid or weak acid? Explain your answer.
     
   • Calculate the concentration of H⁺
   • Calculate the pH of the solution.
   • Calculate the pOH of this solution at 25^oC.
   • Calculate the concentration of hydroxide ions at 25^oC.
   • Explain what impact an increase in hydrogen ion concentration would have on this equation.
     

Colouring Plastics

At a temperature of 30.1^oC and a pressure of about 73.8 bar, carbon dioxide goes into a super critical state that gives the gas solvent-like properties. In this state it can be introduced into polymers, acting as a "carrier" in which dyes, additives, medical compounds and other compounds can be dissolved:

• liquid carbon dioxide is pumped into a high-pressure container with the plastic components to be impregnated
• temperature and pressure are increased steadily until carbon dioxide reaches its supercritical state
• pressure increased to 170bar and the powdered pigment dissolves completely
• the dissolved pigment diffuses with the carbon dioxide gas into the plastic
• high-pressure container is opened, the carbon dioxide gas escapes but the pigment remains attached to the polymer

Tests have shown that nanoparticles of antibacterial agents can be impregnated into polycarbonate and that E-coli bacteria placed on the surface will be killed. Tests conducted with silica and with the anti-inflammatory active pharmaceutical ingredient flurbiprofen were also successful.

The process is suitable for use with amorphous or partially crystalline polymers such as nylon and polycarbonate, but cannot be applied to crystalline polymers.

Reference
Fraunhofer-Gesellschaft (2011, January 4). Impregnating plastics with carbon dioxide. ScienceDaily. Retrieved January 10, 2011, from http://www.sciencedaily.com­ /releases/2011/01/110103110206.htm

Further Reading
Temperature Conversions
Chemical and Physical Changes
Lewis Structures
Molecule Polarity
Intermolecular Forces
Ideal Gas Law

Study Questions:

1. Convert the information provided in the dot points in the article into a flow chart.
   
2. Give the molecular formula for carbon dioxide.
3. Draw a Lewis Structure (electron dot diagram) for carbon dioxide.
4. Is carbon dioxide a polar or non-polar molecule? Explain your answer
5. What type of solvents would be the best to use to dissolve carbon dioxide?
6. What type of solutes do you expect to dissolve in carbon dioxide? Explain your answer.
7. Given that 1bar is equivalent to 100kPa, convert the following pressures in bars to pressures in atmospheres:
   
   • 73.8bar
   • 170bar
8. At 25^oC and 1 atmosphere pressure, 1 mole of gas has a volume to 24.47L. Assuming ideal gas behaviour, what volume would this gas occupy at 30.1^oC and 73.8bar?
9. Calculate the volume of gas above at the same temperature but at a pressure of 170bar.
10. Calculate the volume per molecule of carbon dioxide gas in question in 9.
11. Do you think it is reasonable to assume ideal gas behaviour at this temperature and pressure? Explain your answer.
12. What do you think the term "supercritical state" as used in this article might mean?
    
    

Carbon Dioxide and Climate Change

Scientists at Utrecht University, working with colleagues at the NIOZ Royal Netherlands Institute for Sea Research and the University of Southampton have been studying one of the hottest episodes of Earth's climate history, the Middle Eocene Climatic Optimum (MECO), which occurred around 40 million years ago in order to understand the relationship between Earth's climate and atmospheric carbon dioxide.

Algae use photosynthesis to harvest the energy of the sun, converting carbon dioxide and water into the organic molecules required for growth. Different isotopes of carbon are incorporated into these molecules depending on the environmental conditions under which algae grow. Ancient climate can therefore be reconstructed by analysing the carbon isotope ratios of molecules preserved in fossilised algae.

Using fossilised algae preserved in sediment cores extracted from the seafloor near Tasmania, Australia, by the Ocean Drilling Program, the scientists refined their estimates of carbon dioxide levels using information on the past marine ecosystem derived from studying changes in the abundance of different groups of fossil plankton.

Their analyses indicate that MECO carbon dioxide levels must have at least doubled over a period of around 400,000 years. In conjunction with these findings, analyses using two independent molecular proxies for sea surface temperature show that the climate warmed by between 4 and 6^oC over the same period, suggesting that increased amounts of carbon dioxide in the atmosphere played a major role in global warming during the MECO.

The rapid increase in atmospheric carbon dioxide levels around 40 million years ago approximately coincides with the rise of the Himalayas and may be related to the disappearance of an ocean between India and Asia as a result of plate tectonics, the large scale movements of the Earth's rocky shell (lithosphere).

References:

1. P. K. Bijl, A. J. P. Houben, S. Schouten, S. M. Bohaty, A. Sluijs, G.-J. Reichart, J. S. Sinninghe Damste, H. Brinkhuis. Transient Middle Eocene Atmospheric CO2 and Temperature Variations. Science, 2010; 330 (6005): 819 DOI: 10.1126/science.1193654
2. P. N. Pearson. Increased Atmospheric CO2 During the Middle Eocene. Science, 2010; 330 (6005): 763 DOI: 10.1126/science.1197894

Further Reading
http://www.ausetute.com.au/greenhouse.html
http://www.ausetute.com.au/ccycle.html
http://www.ausetute.com.au/carbon14.html
http://www.ausetute.com.au/isotopes.html

Study Questions

1. Write a chemical equation showing the conversion of atmospheric carbon dioxide into glucose by photosynthesis.
2. Explain what is meant by the term isotope.
3. Give the names and symbols of the three naturally occurring isotopes of carbon.
4. Which isotope of carbon is the most abundant?
5. Which isotopes of carbon are stable?
6. Which isotopes of carbon are unstable (radioactive)?
7. Write a nuclear decay equation for the unstable carbon isotope(s).
8. Explain how ancient climate can be reconstructed by analysing the carbon isotope ratios of molecules preserved in fossilised algae.

Carbon Capture and Storage (CCS)

Combustion of fossil fuels, such as coal, fuel oil, or natural gas, liberates large quantities of carbon dioxide, a gas that significantly affects global climate. A key technology that would reduce emissions and lead to more environmentally friendly power plants is the capture and storage of carbon dioxide from flue gases of power plants (carbon capture and storage (CCS)). CCS might be able to reduce CO₂ emissions resulting from the employment of fossil fuels for power generation and other uses in industry to near zero and thereby contribute to reducing greenhouse-gas emissions.
The Technische Universität Darmstadt has dedicated a pilot plant for capturing carbon dioxide contained in flue gases of power plants using two new methods:

• carbonate looping
• chemical looping

Carbonate looping involves utilizing naturally occurring limestone to initially bind CO₂ from the stream of flue gases transiting power plants' stacks in a first-stage reactor. The resultant pure CO₂ is re-liberated in a second reactor and can then be stored. The advantage of the carbonate-looping method is that even existing power plants can be retrofitted with this new method.

Chemical looping allows CO₂ to be captured with hardly any loss of energy efficiency. Under this method, a dual-stage, flameless, combustion yields a stream of exhaust gases containing only CO₂ and water vapor. The CO₂ can then be captured and stored.

Reference
Technische Universität Darmstadt (2010, November 7). On the way to CO₂-free power plants. ScienceDaily. Retrieved November 8, 2010, from http://www.sciencedaily.com­ /releases/2010/11/101103082306.htm

Further Reading
http://www.ausetute.com.au/combusta.html
http://www.ausetute.com.au/idealgas.html
http://www.ausetute.com.au/heatcomb.html
http://www.ausetute.com.au/greenhouse.html
http://www.ausetute.com.au/ccycle.html

Study Questions

1. Explain what is meant by the term fossil fuel.
2. Write a balanced chemical equation to represent the complete combustion of coal.
3. Write a balanced chemical equation to represent the complete combustion of natural gas.
4. If you burnt 1kg of coal and 1kg of natural gas, which reaction would produce the greatest amount of carbon dioxide?
5. If you burnt 1000cm³ of solid coal, and 1000cm³ of gaseous methane, which reaction would produce the greatest amount of gaseous carbon dioxide?
6. The heat of combustion of methane is 890 kJ/mol. Is energy released or absorbed during this reaction?
7. When coal burns it releases energy, about 250 kJ/mol. At 25^oC and 1 atmosphere pressure, is methane or coal the better fuel?
8. What benefits are there in storing the carbon dioxide emitted during power generation?
9. What disadvantages are there in storing carbon dioxide emitted during power generation?
10. What impact could the storage of this carbon dioxide have on the natural carbon cycle?
    

Dry Water

Discovered in 1968, "dry water" consists of 95% water, yet it is a dry powder which resembles powdered sugar at room temperature and pressure. Each powder particle contains a water droplet surrounded by modified silica. The silica coating prevents the water droplets from combining and turning back into liquid water. The result is a fine powder that can slurp up gases which combine with the water molecules to form hydrates.

Dry water can absorb over three times as much carbon dioxide gas as ordinary uncombined water and silica in the same length of time. This ability to absorb large amounts of carbon dioxide gas as a hydrate could make it useful in helping to reduce global warming since carbon dioxide gas is a major contributor to global warming.

Dry water can also be used to store methane, a component of natural gas. This could provide a safer, more convenient way to store methane fuel for use in vehicles powered by natural gas.

Reference:
American Chemical Society (2010, August 25). 'Dry water' could make a big splash commercially. ScienceDaily. Retrieved August 26, 2010, from http://www.sciencedaily.com­ /releases/2010/08/100825174102.htm

Study Questions

1. Write the chemical formula for each of the following compounds:


• water


• silica


• carbon dioxide


• methane




2. Draw a diagram to represent the molecular structure of dry water powder.
3. Draw a diagram to represent the structure of hydrated carbon dioxide.
4. Explain how water can absorb carbon dioxide.
5. Explain how silica can absorb carbon dioxide.
6. Explain why dry water is so much better at absorbing carbon dioxide than either pure water or silica.
7. Write a chemical equation to represent the production of hydrated methane.
8. Using the equation above, discuss how dry water could be used to store and release methane for use in vehicles powered by natural gas.
   

Champagne Bubbles

Tiny bubbles are the essence of fine champagnes and sparkling wines.
The bubbles, formed during the release of large amounts of dissolved carbon dioxide, help transfer the taste, aroma, and mouth-feel of champagne. Scientists have thought that the act of pouring a glass of champagne could have a big impact on gas levels in champagne and its quality.
Scientists in France have studied carbon dioxide loss in champagne using two different pouring methods:

• pouring champagne straight down the middle of a glass
• pouring champagne down the side of an angled glass

They found that pouring champagne down the side of an angled glass preserved up to twice as much carbon dioxide in champagne compared to pouring it straight down the middle.
They also showed that cooler temperatures help reduce carbon dioxide loss.

Reference:
Liger-Belair et al. On the Losses of Dissolved CO2 during Champagne Serving. Journal of Agricultural and Food Chemistry, 2010; 58 (15): 8768 DOI: 10.1021/jf101239w

Study Questions

1. What is the formula for carbon dioxide?
2. Is carbon dioxide a polar or non-polar molecule?
3. What is the structural formula for ethanol?
4. Is ethanol a polar or non-polar molecule?
5. Would you expect carbon dioxide to dissolve in ethanol? Explain your answer.
6. Describe an experiment you could conduct to test the hypothesis that cooler temperatures reduce carbon dioxide loss in champagne.