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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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Predicting Molecular Polarity

A molecule is considered to be polar, or to have a molecular polarity, when the molecule has an overall imbalance of charge. That is, the molecule has a region with a partial positive charge, and a region with a partial negative charge.


Surprisingly, not all molecules with polar bonds are polar molecules.
 

For example, a carbon dioxide molecule has two polar C=O bonds, but it is not a polar molecule. On the other hand, a water molecule has two polar O-H bonds, and it is a polar molecule.
  

To determine molecular polarity, we must consider the shape of the molecule and the bond dipoles within the molecule.

 If equal bond dipoles act in opposite directions in three-dimensional space, they counteract each other.

  A molecule with identical polar bonds that point in opposite directions is not polar.

  Let us have two examples, carbon dioxide and carbon tetrachloride.

Carbon dioxide, CO2, has two polar C=O bonds acting in opposite directions, so the molecule is non-polar. Carbon tetrachloride, CCl4, has four polar C-Cl bonds in a tetrahedral shape.


We can prove mathematically that four identical dipoles, pointing toward the vertices of a tetrahedron, counteract each other exactly.Therefore, carbon tetrachloride is also non-polar.


By..
Anjani Kumar Singh.

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