--%>
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 : Molecular crystals Among the below

    Among the below shown which crystal will be soft and have low melting point: (a) Covalent  (b) Ionic  (c) Metallic  (d) MolecularAnswer: (d) Molecular crystals are soft and have low melting point.

    		•
  • Q : Moles of chloride ion Select the right

    Select the right answer of the question. A solution of CaCl2 is 0.5 mol litre , then the moles of chloride ion in 500ml will be : (a) 0.25 (b) 0.50 (c) 0.75 (d)1.00

    		•
  • Q : Quantum Mechanical Operators The

    The quantum mechanical methods, illustrated previously by the Schrödinger equation, are extended by the use of operators. Or, w

    		•
  • 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 : Cations Chromium(III) hydroxide is

    Chromium(III) hydroxide is highly insoluble in distilled water but dissolves readily in either acidic or basic solution. Briefly explain why the compound can dissolve in acidic or in basic but not in neutral solution. Write appropriate equations to support your answer

    		•
  • Q : Solubility product On passing H 2 S gas

    On passing H2S gas through a particular solution of Cu+ and Zn+2 ions, first CuS is precipitated because : (a)Solubility product of CuS is equal to the ionic product of ZnS (b) Solubility product of CuS is equal to the solubility product

    		•
  • Q : Partial vapour pressure of volatile

    Choose the right answer from following. For a solution of volatile liquids the partial vapour pressure of each component in solution is directly proportional to: (a) Molarity (b) Mole fraction (c) Molality (d) Normality

    		•
  • 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 : Benefits of soapy detergents over the

    What are the benefits of soapy detergents over the soap less detergents? Briefly state the benefits?

    		•
  • Q : Ddd 4) The addition of S2- ion to

    4) The addition of S2- ion to Fe(OH)2(s). Explain why the addition of S2- ion to Cr(OH)3(s) does not result in the formation of Cr2S3(s).

    		•