--%>
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 : Question on Raoults law Give me answer

    Give me answer of this question. For a dilute solution, Raoult's law states that: (a) The lowering of vapour pressure is equal to mole fraction of solute (b) The relative lowering of vapour pressure is equal to mole fraction of solute (c) The relative lowering of v

    		•
  • Q : Calculate molarity of a solution

    Provide solution of this question. Molarity of a solution prepared by dissolving 75.5 g of pure KOH in 540 ml solution is: (a) 3.05 M (b) 1.35 M (c) 2.50 M (d) 4.50 M

    		•
  • Q : What are electromotive force in

    The main objective of this particular aspect of Physical Chemistry is to examine the relation between free energies and the mechanical energy of electromotive force of electrochemical cells. The ionic components of aqueous solutions can be treated on the basis of the

    		•
  • Q : Mole fraction of water Give me answer

    Give me answer of this question. A solution contains 25%H2O 25%C2H5OH , and 50% CH3 COOH by mass. The mole fraction of H2O would be: (a) 0.25 (b) 2.5 (c) 0.503 (d) 5.03.

    		•
  • Q : Reaction of calcium carbonate Give me

    Give me answer of this question. What is the volume of 0.1NHcl required to react completely with 1.0g of pure calcium carbonate : (Ca= 40, C= 12 and o = 16 ) (a)150cm3 (b)250cm3 (c)200cm3 (d)100cm3

    Q : Strength of the Hydrochloric acid

    Provide solution of this question. 1.0 gm of pure calcium carbonate was found to need 50 ml of dilute HCL for complete reaction. The strength of the HCL solution is specified by : (a) 4 N (b) 2 N (c) 0.4 N (d) 0.2 N

    		•
  • Q : Surface Tension Vapour Pressure The

    The vapor pressure of small liquid drops depends on the drop size. Although the surface properties of a liquid are different from those of the bulk liquid, the special surface properties can be ignored except in a few situations. One is the case in which a liquid is dispersed into fine dr

    		•
  • Q : Mass percent Help me to go through this

    Help me to go through this problem. 10 grams of a solute is dissolved in 90 grams of a solvent. Its mass percent in solution is : (a) 0.01 (b) 11.1 (c)10 (d) 9

    		•
  • Q : Vapour pressure related question Help

    Help me to solve this question. Which of the following is incorrect: (a) Relative lowering of vapour pressure is independent (b)The vapour pressure is a colligative property (c)Vapour pressure of a solution is lower than the vapour pressure of the solvent (d)The

    		•
  • Q : Mole fraction of hydrogen Give me

    Give me answer of this question. In a mixture of 1 gm H2 and 8 gm O2 , the mole fraction of hydrogen is: (a) 0.667 (b) 0.5 (c) 0.33 (d) None of these

    		•