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CHEMISTRY CBSE CLASS X
A compound made up of hydrogen and carbon only . Natural source is petroleum.
Two types-- Saturated ; unsaturated
1. Saturated Hydrocarbons (Alkanes)
Carbon atoms are connected with single covalent bonds and end with ‘ane’. They are unreactive.
The general formula is CnH2n+2
2. Unsaturated Hydrocarbons (Alkenes and Alkynes)
Carbon atoms are connected by a ‘double bond’ or a ‘triple bond’ .These are obtained mostly from petroleum by a process called cracking.
- Alkenes --- CnH2n
Alkenes contain a double bond between two carbon atoms which is formed by sharing of two electron pairs. Simplest alkene is Ethene.
- Alkynes --- CnH2n-2
Alkynes contain a triple bond between two carbon atoms which is formed by sharing of three electron pairs. Simplest Alkyne is Ethyne whose common name is Acetylene.
- Alkyl Groups ---- CnH2n+2
The group formed by the removal of one hydrogen atom from an alkane molecule .
Methyl group (CH3-) is formed by the removal of one H atom from Methane (CH4) , etc.
- Cyclic Hydrocarbons -----
Hydrocarbons in which the carbon atoms are arranged in the form of a ring. They may be saturated or unsaturated.
- A saturated cyclic hydrocarbon is ‘cyclohexane’ – C6H12
Electron dot structure is obtained by putting two electron dots in place of every single bond in its structural formula.
Cyclopropane - C3H6
Cyclobutane – C4H8
Cyclopentane - C5H10
General formula of cycloalkanes is CnH2n
- An unsaturated cyclic hydrocarbon is ‘ benzene’ ( aromatic compounds ) whose electron dot structure is -- 2 electrons in place of every single bond and 4 electrons in place of every double bond in its structural formula.
Single bond -- 2 shared electrons
Double bond -- 4 shared electrons
Naming Hydrocarbons -
|1 carbon atom
- Isomers :- The organic compounds having the same molecular formula but different structures.
- Normal butane has a straight line structure whereas iso-butane structure has a branched chain structure.
- Isomerism is possible only with hydrocarbons having 4 or more carbon atoms ie. Isomerim is not possible in methane, ethane and propane.
- 1st isomer is called n- pentane (normal)
- 2nd isomer is called isopentane
- 3rd isomer is called neopentane
CBSE Important Questions Class X Chemistry By : Mrs. Kritika Bhola
Submitted By Mrs. Kritika Bhola
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