--%>
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 : How can enzymes act as catalyst?

    Enzymes are complex proteinous substances, produced by living bodies, such as act as catalysis in the physiological reactions. The enzymes are, also called biochemical catalysts and the phenomenon is known as bio-chemical catalysis because numerous reactions that occur the bodies of animals and p

    		•
  • Q : Coagulation what is the meaning of

    what is the meaning of fourth power of valency of an active ion?

    		•
  • Q : What is depression in freezing point?

    Freezing point of a substance is the temperature at which solid and liquid phases of the substance coexist. It is defined as the temperature at which its solid and liquid phases have the same vapour pressure. The freezing point o

    		•
  • Q : Explain Second Order Rate Equations.

    Integration of the second order rate equations also produces convenient expressions for dealing with concentration time results.A reaction is classified as second order if the rate of the reaction is proportional to the square of the concentration of one o

    		•
  • Q : Problem on molality Select the right

    Select the right answer of the question. Calculate the molality of 1 litre solution of 93% H2SO4 (weight/volume). The density of the solution is 1.84 g /ml : (a) 10.43 (b) 20.36 (c) 12.05 (d) 14.05

    		•
  • Q : Explain the process of coagulation of

    Presence of small concentrations of appropriate electrolyte is necessary to stabilize the colloidal solutions. However, if the electrolytes are present in higher concentration, then the ions of the electrolyte neutralize the charge on the colloidal particles may unite

    		•
  • Q : What is electrolytic dissociation? The

    The Debye Huckel theory shows how the potential energy of an ion in solution depends on the ionic strength of the solution.Except at infinite dilution, electrostatic interaction between ions alters the properties of the solution from those excepted from th

    		•
  • Q : Molar mass Select the right answer of

    Select the right answer of the question. Which is heaviest: (a)25 gm of mercury (b)2 moles of water (c)2 moles of carbon dioxide (d)4 gm atoms of oxygen

    		•
  • Q : Benzoic acid is weaker than paranitro

    Briefly state that Benzoic acid is weaker than paranitro benzoic acid?

    		•
  • Q : Problem on physical and thermodynamic

    The shells of marine organisms contain calcium carbonate CaCO3, largely in a crystalline form known as calcite. There is a second crystalline form of calcium carbonate known as aragonite. Physical and thermodynamic properties of calcite and aragonite at 298

    		•