Which functional group is present in alcohol?

$(a)$ Write chemical equations for the reactions of ethanoic acid with:
$(i)$ Sodium
$(ii)$ Sodium carbonate
$(iii)$ Ethanol in the presence of conc. $H_{2}SO_{4}$.
$(b)$ State the role of concentrated sulphuric acid in the esterification reaction.
$(c)$ Write one use of ethanoic acid.

Explain why washing clothes with hard water is not effective.

$(i)$ Give one example with a chemical equation for the following reactions:
$(a)$ Substitution reaction.
$(b)$ Saponification reaction.
$(c)$ Combustion reaction.

List two characteristic features of carbon which,when put together,give rise to a large number of carbon compounds.

$A$ carboxylic acid (molecular formula $C_{2}H_{4}O_{2}$) reacts with an alcohol in the presence of an acid catalyst to form a compound $'X'$. The alcohol on oxidation with alkaline $KMnO_{4}$ followed by acidification gives the same carboxylic acid $C_{2}H_{4}O_{2}$. Write the name and structure of $(i)$ carboxylic acid,$(ii)$ alcohol,and $(iii)$ the compound $'X'$.