(A) (i) (a) $\mathrm{H}-\underset{\underset{\mathrm{H}}{|}}{\overset{\stackrel{\mathrm{H}}{|}}{\mathrm{C}}}-\underset{\underset{\mathrm{H}}{|}}{\overset{\stackrel{\mathrm{H}}{|}}{\mathrm{C}}}-\underset{\underset{\mathrm{H}}{|}}{\overset{\stackrel{\mathrm{H}}{|}}{\mathrm{C}}}-\stackrel{\stackrel{\mathrm{O}}{\left|\right|}}{\mathrm{C}}-\mathrm{OH}$
(b) $\mathrm{H}-\underset{\underset{\mathrm{H}}{|}}{\overset{\stackrel{\mathrm{H}}{|}}{\mathrm{C}}}-\underset{\underset{\mathrm{H}}{|}}{\overset{\stackrel{\mathrm{H}}{|}}{\mathrm{C}}}-\underset{\underset{\mathrm{H}}{|}}{\overset{\stackrel{\mathrm{H}}{|}}{\mathrm{C}}}-\underset{\underset{\mathrm{H}}{|}}{\overset{\stackrel{\mathrm{Cl}}{|}}{\mathrm{C}}}-\underset{\underset{\mathrm{H}}{|}}{\overset{\stackrel{\mathrm{H}}{|}}{\mathrm{C}}}-\mathrm{H}$
(ii) Both are isomers of compound with chemical formula ${\mathrm{C}}_6{\mathrm{H}}_{14}$. Structure (i) is 2,3-dimethylbutane whileStructure (ii) is 2,2-dimethylbutane. One more isomer is, 3-methylpentane.
(iii) Saturated carbon compounds always follow the general formula of ${\mathrm{C}}_{\mathit{n}}{\mathrm{H}}_{2\mathit{n}+2}$. In case of unsaturated carbon compounds, they always follow the general formula ${\mathrm{C}}_{\mathit{n}}{\mathrm{H}}_{2\mathit{n}}$ if there is a carbon-carbon double bond and formula ${\mathrm{C}}_{\mathit{n}}{\mathrm{H}}_{2\mathit{n}-2}$ if there is a carbon-carbon triple bond.
OR
(B) (i) Alcohols react with sodium leading to the evolution of hydrogen.
(ii) The melting point of pure ethanoic acid is $290\mathrm{K}$ and hence it often freezes during winter in cold climates. This gave rise to its name glacial acetic acid.
(iii) Heating ethanol at $443\mathrm{K}$ with excess concentrated sulphuric acid results in the dehydration of ethanol to give ethene. In this case, concentrated sulphuric acid act as a dehydrating agent as at removes water from ethanol.
ethanol.
(iv) On treating with sodium hydroxide, which is an alkali, the ester is converted back to alcohol and sodium salt of carboxylic acid. This reaction is known as saponification because it is used in the preparation of soap. Soaps are sodium or potassium salts of long chain carboxylic acid.