Butanone is a four-carbon compound with the functional group:

Which is the functional group in propanone?

Write the molecular formula of an alcohol that can be derived from butane.

$(i)$ Distinguish between saturated hydrocarbons and unsaturated hydrocarbons with the help of the combustion process.
$(ii)$ Write the chemical names of $C_{4}H_{10}$ and $C_{2}H_{2}$ and draw their structures.

What is meant by homologous series of carbon compounds? Classify the following carbon compounds into two homologous series and name them.
$C_{3}H_{4}, C_{3}H_{6}, C_{4}H_{6}, C_{4}H_{8}, C_{5}H_{8}, C_{5}H_{10}$

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