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Question
Write the first four members of the homologous series that begins with H-C≡C-H. Also, write down their general molecular formula.
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Solution
| No. | Name of a compound and molecular formula | Structural formula |
| 1. | Ethyne (C2H2) | HC ≡ CH |
| 2. | Propyne (C3H4) | CH3 - C ≡ CH |
| 3. | But-1-yne (C4H6) | CH3 - CH2 - C ≡ CH |
| 4. | Pent-1-yne (C5H8) | CH3 - CH2 - CH2 - C ≡ CH |
Comparing these molecular formulae and assigning the number of carbon atoms as ‘n’, the following general formula is deduced: CnH2n - 2 (where n = 2, 3, 4...)
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