Which of the following are carboxylic acids:
C2H4O2, C2H4O, C2H6O, C3H6O2?
Carboxylic acids are compounds where one or more hydrogen atoms are replaced by the -COOH group:
Note that every carboxylic acid contains 2 O (oxygen) atoms. The carboxylic acids with no other functional groups have the molecular formula CnH2nO2.
Using this, one can say that C2H4O2 (ethanoic acid) and C3H6O2 (propanoic acid) are carboxylic acids.