--%>
Assignment Help - homework help

Explain oxygen and its preparation.

Karl Scheele, the Swedish chemist, was the first to prepare oxygen by heating mercuric oxide in 1772. He recognized the gas as one of the major constituents of atmospheric air and called it 'fire air'. Joseph Priestley, the English chemist also prepared oxygen by focusing the sun rays by means of a double lens on mercuric oxide. Priestley published his results in 1774 and has been regarded as the discoverer of oxygen. However, its elemental nature was proved by Lavoisier.

Oxygen is first element of group 16 of periodic table. It may be called the head of chalcogens family. Its configuration (1s22s22p4)shows the presence of six electrons in the valence shell. It does show some characteristics which are not shown by other members of the family because of its small size. For example, it is able to form pπ-pπ bonding and exists as diatomic molecule (O2). The other elements of the group do not exist as diatomic molecule due to their inability to form pπ-pπ bonding.

Isotopes of oxygen

Oxygen has three naturally occurring isotopes which are:

1870_dioxygen.png 

Out of these three isotopes, O-18 is radioactive in nature and finds frequent use in studying the mechanisms of organic reactions and other trace techniques. Like hydrogen, oxygen also exists in the elementary form as diatomic molecule (O2) and is referred to as dioxygen. 

Terrestrial abundance and distribution

Oxygen is the most abundant element on the surface of the earth. In Free State, it occurs in air and constitutes 21% by volume of air and 23% by weight. In the combined state, it constitutes 89% by mass of water and 50% by mass of earth's solid crust. In earth's solid crust, it is mainly present as silicates, carbonates, aluminates and oxides of metals.

Almost all the dioxygen in atmosphere is believed to be the result of photosynthesis by green plants which can be represented as 

1915_dioxygen1.png 

   Related Questions in Chemistry

  • Q : What are methods of phenol preparation

    Phenol was initially obtained by fractional distillation of coal

    		•
  • Q : Colligative effect Choose the right

    Choose the right answer from following. Which one of the statements written below concerning properties of solutions, explain a colligative effect: (a) Boiling point of pure water decreases by the addition of ethano (b) Vapour pressure of pure water d

    		•
  • Q : Eutectic Formation In some two

    In some two component, solid liquid systems, a eutectic mixture forms.Consider, now a two component system at some fixed pressure, where the temperature range treated is such as to include formation of one or more solid phases. A simple behavior is shown b

    		•
  • Q : Problem on bubble point The following

    The following mixture of hydrocarbons is obtained as one stream in a petroleum refinery.

    Q : Describe Transformation Matrices. Each

    Each symmetry operation can be represented by a transformation matrix.You have seen what happens when a molecule is subjected to the symmetry operation that corresponds to any of the symmetry elements of the point group to which the molecule belongs. The m

    		•
  • Q : Sedimentation and Velocity The first

    The first method begins with a well defined layer, or boundary, of solution near the center of rotation and tracks the movement of this layer to the outside of the cell as a function of time. Such a method is termed a sedimentary velocity experiment. A

    		•
  • Q : Question on seminormal solution Provide

    Provide solution of this question. The weight of sodium carbonate required to prepare 500 ml of a seminormal solution is: (a) 13.25 g (b) 26.5 g (c) 53 g (d) 6.125 g

    		•
  • Q : Concentration of Sodium chloride

    Provide solution of this question. If 25 ml of 0.25 M NaCl solution is diluted with water to a volume of 500ml the new concentration of the solution is : (a) 0.167 M (b) 0.0125 M (c) 0.833 M (d) 0.0167 M

    		•
  • Q : Colligative properties give atleast two

    give atleast two application of following colligative properties

    		•
  • Q : Describe Point Groups. For any

    For any symmetric object there is a set of symmetry operations that, together, constitute a mathematical group, called a point group.It is clear from the examples that most molecules have several elements of symmetry. The H2O

    		•