Q.

1. What is meant by homologous series? Write the first four members of homologous series that begins with
   A. CH3CHO
   B. H-C≡C-H
   Also write down their general molecular formula.

Step 1. Definition (section 14.3.2). A homologous series is a series of compounds of the same functional-group family in which each member shares the same type of carbon skeleton and functional group, and differs from the next member by exactly one -CH2- (methylene) unit in both molecular and structural formula; every member (homologue) fits one shared general molecular formula.

Step 2A. Series beginning at CH3CHO (acetaldehyde, an aldehyde, n=2 of the CnH2nO series -- Table 14.4's own pattern). Adding -CH2- successively: CH3CHO (ethanal) -> CH3-CH2-CHO (propanal) -> CH3-CH2-CH2-CHO (butanal) -> CH3-CH2-CH2-CH2-CHO (pentanal). General molecular formula: CnH2nO. …

Applying section 14.3.2's homologous-series definition (successive -CH2- addition, one shared general formula) directly, following th …

• Starting the count from methane/ethyne rather than from the actually-given starting compound (CH3CHO / HC≡CH) when listing 'the first four members' of THIS particular series. …