Which substance is produced by the oxidation of methanal in the presence of an oxidising agent?

Match the reactions given in Column $(A)$ with the names given in Column $(B).$

Column $(A)$	Column $(B)$
$(a)$ $CH_{3}OH + CH_{3}COOH \xrightarrow{H^{+}} CH_{3}COOCH_{3} + H_{2}O$	$(i)$ Addition reaction
$(b)$ $CH_{2}=CH_{2} + H_{2} \xrightarrow{Ni} CH_{3}-CH_{3}$	$(ii)$ Substitution reaction
$(c)$ $CH_{4} + Cl_{2} \xrightarrow{\text{Sunlight}} CH_{3}Cl + HCl$	$(iii)$ Neutralisation reaction
$(d)$ $CH_{3}COOH + NaOH \longrightarrow CH_{3}COONa + H_{2}O$	$(iv)$ Esterification reaction

$CH_{3}COOH + C_{2}H_{5}OH \xrightarrow[\Delta]{\text{conc. } H_{2}SO_{4}} (?)$

Both soap and detergent are some type of salts. What is the difference between them? Describe in brief the cleansing action of soap. Why do soaps not form lather in hard water? List two problems that arise due to the use of detergents instead of soaps.

Which among the following are unsaturated hydrocarbons?
$(i)$ $H_3C-CH_2-CH_2-CH_3$
$(ii)$ $H_3C-C\equiv C-CH_3$
$(iii)$ $H_3C-CH(CH_3)-CH_3$
$(iv)$ $H_3C-C(CH_3)=CH_2$

Chlorine reacts with saturated hydrocarbons at room temperature in the :