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CHEMISTRY CBSE CLASS X
A group of organic compounds having similar structures and similar chemical properties in which the successive compounds differ by CH2 group.
Two adjacent homologous groups differ by 1 carbon atom and 2 hydrogen atoms .
General formula of Alkanes --- CnH2n+2
Characteristics of a Homologus Series
- All members represented by same general formula.
- Two adjacent homologues differ by a CH2
- Difference between molecular masses of any 2 homologues is 14 μ
- All compounds show similar chemical properties.
- There is gradual change in their physical properties with increase in molecular masses. (melting , boiling points and densities increase)
Alkenes --- CnH2n
Alkynes --- CnH2n-2
Functional Groups –
An ‘atom’ or a ‘group of atoms’ which makes a carbon compound reactive and decides its properties.
- Halo Group : − X (X can be Cl, Br or I)
Chloro , Bromo and Iodo group ----
When 1 H atom of an alkane is replaced by a halogen atom, we get Haloalkane.
Eg. CH4 → Replace one H by Cl → CH3Cl
General formula is CnC2n+1 –X ( X may be Cl ; Br; I )
Chloromethane - CH3Cl ---- methyl chloride
Bromomethane - CH3Br ---- methyl bromide
Chloroethane - C2H5Cl ---- ethyl chloride
Chloropropane - C3H7Cl ---- propyl chloride
- Alcohol Group : −OH ( alcoholic / hydroxyl group)
Alcohol group is made up of 1 oxygen and 1 hydrogen atom joined together.
1 H atom is replaced by an alkane by a hydroxyl group ( OH group)
CH4 → Replace 1 H by OH → CH3OH
General formula is CnC2n+1OH
Methanol - CH3OH ---- methyl alcohol
Ethanol - C2H5OH ---- ethyl alcohol
Propanol - C3H5OH ---- propyl alcohol
CBSE Important Questions Class X Chemistry By : Mrs. Kritika Bhola
Submitted By Mrs. Kritika Bhola
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