Assignments in Science Class X (Term II)
Carbon and its Compounds
9. Unsaturated organic compounds : Organic compounds in which a double or a triple bond exists between two carbon atoms in a carbon chain, are called unsaturated organic compounds. 10. Hydrocarbons : Organic compounds which contain only carbon and hydrogen atoms are called hydrocarbons. 11. Straight chain hydrocarbons : Hydrocarbons, in which all the carbon atoms are linked to one another in a straight chain by a single covalent bond are called straight chain hydrocarbons. 12. Branched chain hydrocarbons : Hydrocarbons, in which one or more carbon atoms are attached to the main straight chain of carbon atoms by a single covalent bond are called branched chain hydrocarbons. 13. Isomerism : The phenomenon due to which there can exist two or more organic compounds, with different physical and chemical properties, due to the difference in arrangement of carbon atoms in their structure, but have same chemical formula is called isomerism. 14. Homologous series : A group of members of the same class of organic compounds, which differ from each other by a – CH2 group, when arranged in the ascending order of molecular mass, is called a homologous series. 15. Homologous : The members of the same class of organic compounds, when arranged in the ascending order of molecular mass, such that they differ by 14 amu or a – CH2 group are called homologous. 16. Alkanes (saturated hydrocarbons) : Compounds of carbon and hydrogen, in which all the valencies of carbon atoms are satisfied by single covalent bonds are called saturated hydrocarbons or alkanes.
1. Covalent bond or Molecular bond or Homopolar bond : A chemical bond formed between two non-metallic elements by the mutual sharing of one or more electron pairs is called covalent bond. 2. Covalency : The number of electron pairs which an atom of an element mutually shares with another atom or atoms of the same or different elements, so as to acquire a stable configuration like noble gases, is called covalency. 3. Properties of covalent (molecular) compound : (i) They have low melting point and boiling point. (ii) They have low density, i.e., their density is generally less than that of water. (iii) They are gaseous or volatile liquids or soft solids. (iv) They are insoluble in water, but soluble in organic solvents. (v) They are generally bad conductors of electricity. 4. Diamond is the purest crystalline form of carbon which is the hardest naturally occurring substance.
5. Other pure crystalline forms of carbon are graphite and fullerenes. In Buckminsterfullerene, each molecule has 60 atoms arranged in hexagons and pentagons. 6. Organic Chemistry : The branch of chemistry dealing with carbon compounds other than carbon monoxide, carbon dioxide and carbonates is called organic chemistry. 7. Catenation : The property of carbon atoms to link with other carbon atoms or the atoms of other elements with single, double or triple covalent bonds, so as to form large number of compounds is called catenation. 8. Saturated organic compounds : Organic compounds in which all the four valencies of carbon atoms are satisfied by single covalent bonds, are called saturated organic compounds. 1
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General formula for alkanes is CnH2n + 2 where ‘n’ stands for number of carbon atoms. 17. Alkenes : A homologous series of unsaturated hydrocarbons, characterised by the presence of double covalent bond (— C = C —) in the
straight chain of carbon atoms, are called alkenes. General formula for alkenes is CnH2n where n stands for the number of carbon atoms in the carbon chain. 18. Alkynes : A homologous series of hydrocarbons, characterised by the triple covalent bond (— C ≡ C straight chain of carbon atoms alkynes. unsaturated presence of —) in the are called 25.
General formula for alkynes is CnH2n – 2, where ‘n’ stands for the number of carbon atoms in...
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