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Questions
Write the molecular formula of two consecutive members of homologous series of aldehydes. State which part of these compounds determines their
- physical and
- chemical properties
Write the molecular formula of any two consecutive members of homologous series of aldehydes.
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Solution 1
The molecular formula of two consecutive members of homologous series of aldehydes:-
\[\ce{CH3 - CHO}\] and \[\ce{CH3 - CH2 - CHO}\]
In \[\ce{CH3 - CHO}\] compound, \[\ce{-CHO}\] part and in \[\ce{CH3 - CH2 - CHO}\], \[\ce{-CH2-CHO}\] part will determine their physical and chemical properties.
Solution 2
Two consecutive members:
| Molecular Formula | Structure | |
| Methanal (Formaldehyde) | \[\ce{CH2O}\] | \[\ce{H - CHO}\] |
| Ethanal (Acetaldehyde) | \[\ce{C2H4O}\] | \[\ce{CH3 - CHO}\] |
Notes
Students should refer to the answer according to their questions.
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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 |
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| 1-Pentene | C5H10 | CH3–CH2–CH2–CH = CH2 | ______ | ______ | 30 |
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