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Question
Which of the following does not belong to the same homologous series?
Options
CH4
C2 H6
C3 H8
C4 H8
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Solution
C4 H8
Explanation -
The succeeding members of the homologues series differ by a —CH2 - unit. The general formula for the alkane is CnH2n+2. Methane (CH4), ethane (C2H6) and propane (C3H8) are members of homologues series for alkanes while butene (C4H8) is the fourth member of homologues series for alkene.
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| Name | Molecular formula | Condensed structural formula | Number of carbon atom | Number of -CH2- units | Boiling point °C |
| Methanol | CH4O | CH3-OH | 1 | 1 | 63 |
| Ethanol | C2H6O | CH3–CH2-OH | 2 | 2 | 78 |
| Propanol | C3H8O | CH3–CH2–CH2-OH | ______ | ______ | 97 |
| Butanol | C4H10O | CH3–CH2–CH2–CH2–OH | ______ | ______ | 118 |
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| Name | Molecular formula | Condensed structural formula | Number of carbon atom | Number of -CH2- units | Boiling point °C |
| Ethene | C2H4 | CH2 = CH2 | 2 | 0 | -102 |
| Propene | C3H6 | CH3–CH = CH2 | 3 | 1 | -48 |
| 1-Butene | C4H8 | CH3–CH2–CH = CH2 | ______ | ______ | -6.5 |
| 1-Pentene | C5H10 | CH3–CH2–CH2–CH = CH2 | ______ | ______ | 30 |
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| Common name | Marsh gas | 3. ______ |
