What is the common name of propanone?

Name the functional group present in the following compounds:
$(i)$ $CH_{3}-CH_{2}-CH_{2}-COOH$
$(ii)$ $CH_{3}-CO-CH_{2}-CH_{3}$

The correct structural formula of butanoic acid is

Which of the following are the heteroatoms present in $CH_{3}-CH_{2}-O-CH_{2}-CH_{2}Cl$?
$(i)$ Oxygen
$(ii)$ Carbon
$(iii)$ Hydrogen
$(iv)$ Chlorine

What are soaps chemically? How do they differ from synthetic detergents? Explain the mechanism and the cleansing action of soap.

The formula of citric acid is shown below:
$\begin{matrix}
\,\,\,\,\,COOH \\
|\,\,\,\,\,\,\, \\
CH_{2}\, \\
|\,\,\,\,\, \\
HO-C-COOH \\
|\,\,\,\,\, \\
\,CH_{2} \\
|\,\,\,\,\, \\
\,\,\,\,\,\,COOH \\
\end{matrix}$
State the name of the $-COOH$ functional group present in citric acid.