What is the boiling point of propanone (in $;K$)?

What is the common name of $Methanal$?

Which polymer is formed by reacting a compound containing two carboxylic acid groups and a compound containing two hydroxyl groups?

The structural formula of benzene is:

The general formula of three compounds $A, B$ and $C$ is $C_{n}H_{2n}$. $B$ has the highest boiling point and $C$ has the lowest boiling point.
$(i)$ Mention the type of compound $A, B$ and $C$.
$(ii)$ Which of these has the minimum number of carbon atoms?
$(iii)$ Name the homologous series to which $A, B$ and $C$ belong.

State the valency of each carbon atom in $(i)$ an alkane and $(ii)$ an alkyne.