Problem 2 - Combustion of Fossil Fuels

In economies with limited supplies of petroleum and natural gas (which is primarily methane), coal (both bituminous and anthracite) has been a major fuel for power plants. Compare the burning of methane with the burning of either bituminous or anthracite coal in terms of the thermodynamic efficiency, the practicality, and the effects on the environment of these processes.

In 2000 the Citizens Electric Corporation of Ste. Genevieve, Missouri, sold 1.055 x 10⁹ kWh of power from their gas powered plant. How much natural gas was consumed to generage that much power? How much coal would have been required to generate the same amount of power?

Your answer should be illustrated with chemical equations for the relevant reactions and should be as quantitative as possible.

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Kotz, J. C.; Moore, J. W.; Stanitski, C. L.; Wood, J. L. The Chemical World: Concepts and Applications (Second Edition) Harcourt Brace & Company: Toronto, 1998

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Acid Rain
Sources of Acid Rain




















Rain water is slightly acidic due to the presence of the atmospheric carbon dioxide which dissolves into the water droplets to liberate acidic hydrogen cations. Other gases in the atmosphere, however, liberate higher concentrations of hydrogen cations when dissolved in rain water thus cont ributing much greater to the acid rain problem. Acid rain results primarily from the production of sulfur dioxide and nitrogen dioxide that result from the burning of sulfur-containing coal in power-generating plants and automobile emissions. Sulfur dioxide is slowly converted to SO₃ by reaction with oxygen in air, and SO₃ dissolved in rainwater to yield dilute sulfuric acid, H₂SO₄:

S (in coal) + O_{2 (g)} ---> SO_{2 (g)}
2 SO_{2 (g)} + O_{2 (g)} ---> 2 SO_{3 (g)}
SO_{3 (g)} + H₂O _(l) ---> H₂SO_{4 (aq)}

Nitrogen dioxide reacts with water to produce a mixture of nitrous acid and nitric acid:

2 NO_{2 (g)} + H₂O _(l) ---> HNO_{2 (aq)} + HNO_{3 (aq)}


Caption
Bottom left: Sulfur burns in pure oxygen to produce sulfur dioxide, SO₂, which gives off a bright blue flame.

Text
Fay, R. C.; McMurry, J Chemistry: Second Edition Prentice Hall: New Jersey, 1998
Zumdahl, S Chemistry Houghton Mifflin Co.: Boston, 1997

Image
Top right: Kotz, J. C.; Moore, J. W.; Stanitski, C. L.; Wood, J. L. The Chemical World: Concepts and Applications (Second Edition) Harcourt Brace & Company: Toronto, 1998
Bottom left: Kotz, J. C.; Moore, J. W.; Stanitski, C. L.; Wood, J. L. The Chemical World: Concepts and Applications (Second Edition) Harcourt Brace & Company: Toronto, 1998

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Greenhouse Effect
The greenhouse effect is the process through which atmospheric trace gases, known as greenhouse gases (GHGs), cause solar radiation to be trapped and stored on the surface of the Earth as heat. When radiation from the Sun reaches the Earth's surface, most of its energy is absorbed by land and water. This causes the surface to emit infrared radiation, which is then absorbed by GHGs, preventing the heat from leaving the atmosphere.


As a result of greenhouse effect, the average global temperature is rising dramatically. Scientists predict that further warming of the atmosphere will take place over the next century, which will cause an estimated rise in temperature at a rate that is faster than during any other period of time over the last 10 000 years. As we continue to emit large amounts of GHGs, the impact of this climate change on people, economies and the environment will be become more and more severe. The number of significant natural catastrophes such as floods and storms are expected to increase in multiples.

GHG emissions are already linked directly to health impacts and these climate changes will continue to have extremely harmful effects on human health, specifically the loss of life. Air pollution is one of the most visible factors, since the burning of fossil fuels is a major source of air pollutants such as toxic metals and smog.

Text
http://www.climatechangesolutions.com/english/science/default.htm
http://www.science.gmu.edu/~zli/ghe.html

Image
Kotz, J. C.; Moore, J. W.; Stanitski, C. L.; Wood, J. L. The Chemical World: Concepts and Applications (Second Edition) Harcourt Brace & Company: Toronto, 1998

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Combustion
Combustion is the process of combining with oxygen, usually with the release of large amounts of heat and light, often in the form of flame. Burning in air is a common example. O₂ acts as an oxidizing agent in these combustion reactions which are all redox processes.

The exothermic combustion reactions of hydrocarbons and other organic molecules result in the breaking of C-C and C-H bonds and the combining of carbon and hydrogen atoms each with oxygen. The resulting products of complete combustion are CO₂ and H₂O (although CO may form from incomplete combustion). For example, the combustion reaction of the hydrocarbon, butane, which is used in cigarette lighters is

2 C₄H_{10 (g)} + 13 O_{2 (g)} ---> 8 CO_{2 (g)} + 10 H₂O _(g).

Another example is the oxidation of sulfur to produce sulfur dioxide (SO₂):

S _(s) + O_{2 (g)} ---> SO_{2 (g)}

Caption
The flame produced in the combustion reaction of a butane lighter and oxygen is used to light cigarettes.

Text
Silberberg, M. S. Chemistry: Second Edition; McGraw-Hill, Inc.: Toronto, 2000
Fay, R. C.; McMurry, J Chemistry: Second Edition Prentice Hall: New Jersey, 1998

Image
Kotz, J. C.; Moore, J. W.; Stanitski, C. L.; Wood, J. L. The Chemical World: Concepts and Applications (Second Edition) Harcourt Brace & Company: Toronto, 1998

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