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Environmental Chemistry Complete Notes..

Environmental Chemistry Environmental chemistry: It is the branch of chemistry that deals with the study of various chemical processes taking place in the various segments of the environment. Broadly speaking, it is the study of the sources, transportation, reactions, effects and the ultimate of the chemical species occurring in one or more segments of the environment. Components of Environment : Atmosphere:   This comprises a blanket of gaseous layer around earth. Hydrosphere :  This comprises about 96% of earth’s surface & includes all   sources of water like oceans rivers lakes, glaciers, ground water etc. Lithosphere :  It refers to earth’s solid crust containing the outer mineral cover. It comprises soil, minerals, organic matter etc.  Biosphere:   It refers to the domain of living organism in covalent with atmosphere hydrosphere as well as lithosphere.    Environmental pollution...
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Octane numbers



Octane numbers:

Automobile fuels are graded using octane numbers, which measure the combustibility of a fuel. A high octane number means that a fuel requires a higher temperature and/or higher pressure to ignite. Racing cars with high-compression engines usually run on pure methanol, which has an octane number of 120.

 Gasoline with too low an octane number can cause “knocking” in the engine of a car, when the fuel ignites too easily and burns in an uncontrolled manner. Knocking lowers fuel efficiency, and it can damage the engine.

As early as 1925, two of the first automobile engineers became aware of the need to improve the octane number of fuels. Charles Kettering advocated the use of a newly developed compound called tetra-ethyl lead, Pb(C2H5)4. This compound acts as a catalyst to increase the efficiency of the hydrocarbon combustion reaction. Henry Ford believed that ethanol, another catalyst, should be used instead of tetra-ethyl lead. Ethanol could be produced easily from locally grown crops. As we now know, ethanol is also much better for the environment.

Tetra-ethyl lead became the chosen fuel additive. Over many decades, lead emissions from car exhausts accumulated in urban ponds and water systems. Many waterfowl that live in urban areas experience lead poisoning. Lead is also dangerous to human health.

Leaded fuels are now banned across Canada. In unleaded gasoline, simple organic compounds are added instead of lead compounds. These octane-enhancing compounds include methyl-t-butyl ether, t-butyl alcohol, methanol, and ethanol. Like lead catalysts, these compounds help to reduce engine knocking. In addition, burning ethanol and methanol produces fewer pollutants than burning hydrocarbon fuels, which contain contaminants. Since they can be made from crops, these alcohols are a renewable resource.

By:
Anjani Kumar Singh

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