1-y, 2-w, 3-x, 4-z
Formic acid is the simplest carboxylic acid, containing a single carbon atom. It occurs naturally in various sources including the venom of bee and ant stings. Its IUPAC name is methanoic acid- HCOOH.
Vinegar is a 5 to 8 % solution of acetic acid, the second member of the homologous series of carboxylic acid. Its IUPAC name is ethanoic acid- CH3COOH.
Propionic acid, the 3rd member of the homologous series, is found in milk. Its IUPAC name is propanoic acid- CH3CH2COOH.
Butyric acid, the 4th member of the homologous series, is found in butter. Its IUPAC name is butanoic acid- CH3CH2CH2COOH.