What is mixed with natural rubber to obtain vulcanized rubber?

What percentage concentration of an aqueous solution of formaldehyde is known as formalin?

Write the names of the following compounds:
$(a)$ $CH_3-CH_2-CH_2-CH_2-COOH$
$(b)$ $CH_3-CH_2-C \equiv CH$

$A$ 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 $'X'$.

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

Carbon,a Group $14$ element in the Periodic Table,is known to form compounds with many elements. Write an example of a compound formed with:
$(a)$ Chlorine (Group $17$ of Periodic Table)
$(b)$ Oxygen (Group $16$ of Periodic Table)