(i) A homologous series is a series of carbon compounds having the same functional group and similar chemical properties, in which each successive member differs by a –CH₂– unit (14 u).
From the given compounds:
C₂H₄ and C₄H₈ belong to the same homologous series (alkenes).
(ii)
(I) Esterification reaction:
$$\text{CH}_3\text{CH}_2\text{OH} + \text{CH}_3\text{COOH} \xrightarrow{\text{Acid}} \text{CH}_3\text{COOC}_2\text{H}_5 + \text{H}_2\text{O}$$
(Product: Ethyl ethanoate/ester + Water)
(II) Combustion reaction:
$$\text{C}_2\text{H}_5\text{OH} + 3\text{O}_2 \xrightarrow{\text{Burning}} 2\text{CO}_2 + 3\text{H}_2\text{O} + \text{heat and light}$$
(iii) Soap molecules have a hydrophilic (water-loving) head and a hydrophobic (water-repelling) tail. When added to water, the hydrophobic tails cluster inward (away from water) while the hydrophilic heads face outward toward water, forming a spherical cluster called a micelle.
Source: Chapter 4 – Carbon and its Compounds, Sections 4.2, 4.3.1, 4.4.2
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