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Solution :
(b)
(i) A homologous series is a collection of compounds with the same general formula that differ only in the carbon chain length.
Compounds in a homologous series often have a fixed set of functional group, resulting in chemical and physical properties that are comparable.
For example, homologous series of alkane: CH₄, C₂H₆, C₃H₈, etc. are homologous.
They differ from each other by -CH₂ unit (14 u)
Alkynes are hydrocarbons which contain carbon-carbon triple bonds.
Their general formula is C_nH_2n-2 for molecules with one triple bond (and no rings).
Name of 1st member of Alkyne is : C₂H₂
Electron-dot structure of Ethyne is as follows:

(ii) A functional group is defined as an atom or group of atoms within a molecule that has similar chemical properties whenever it appears in various compounds. Even if other parts of the molecule are quite different, certain functional groups tend to react in certain ways.
Formula of functional group of alcohol is : R-OH
Formula of functional group of carboxylic acid is : R-COOH

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Homologous Series of Compounds.

(A)

A homologous series of carbon compounds refers to a group of organic compounds that have a similar structure and exhibit a gradual change in physical and chemical properties as the molecular weight increases. These compounds have the same functional group and differ from each other by a CH2 unit. Examples of homologous series of carbon compounds include alkanes, alkenes, and alkynes.

The general formula for alkynes is CnH2n-2, where n represents the number of carbon atoms in the molecule. The first homologue of this series is ethyne, also known as acetylene, with the molecular formula C2H2.

The electron dot structure of ethyne is:

H-C?C-H

In this structure, each carbon atom is bonded to one hydrogen atom and to each other by a triple bond. The triple bond between the carbon atoms consists of one sigma bond and two pi bonds. The electron dot structure shows that each carbon atom has two unpaired electrons and each hydrogen atom has one unpaired electron.

unctional Groups: Alcohols & Carboxylic Acids

(B)

The functional group in an organic compound is a specific group of atoms that is responsible for the compound's characteristic chemical reactions and properties. It is usually an atom or a group of atoms that determine the compound's reactivity and its physical and chemical properties.

In alcohols, the functional group is the hydroxyl (-OH) group, which is attached to a carbon atom. The general formula for an alcohol is R-OH, where R represents the rest of the molecule.

In carboxylic acids, the functional group is the carboxyl (-COOH) group, which consists of a carbonyl group (-C=O) and a hydroxyl group (-OH) attached to the same carbon atom. The general formula for a carboxylic acid is R-COOH, where R represents the rest of the molecule.