(a) For the definition o functional group, The functional groups present in the compound are: Aldehydic (al) and carboxyl group (oic acid):
(b) Ethanol is oxidised to ethanoic acid. In tthis, dilute alkaline `KMnO_(4)` acts as an oxidising agent.
`underset("Ethanol")(CH_(3)CH_(2)OH)+underset("(released from oxidising agent)")(2(O))tounderset("Ethanoic acid")(CH_(3)COOH)+H_(2)O`