Question

Which of the following are carboxylic acids: 

C₂H₄O₂, 

C₂H₄O, 

C₂H₆O, 

C₃H₆O₂?

Answer 1

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 C_nH_2nO₂. 

Using this, one can say that C₂H₄O₂ (ethanoic acid) and C₃H₆O₂ (propanoic acid) are carboxylic acids.