What functional group is represented by the formula CHO?

The formula CHO corresponds to an aldehyde functional group. In an aldehyde, the carbon atom is bonded to a hydrogen atom and also has a double bond with an oxygen atom, which is collectively referred to as a carbonyl functional group. Aldehydes are characterized by the presence of this carbonyl group at the end of a carbon chain, giving them their distinct properties.

In contrast, an amide contains a carbonyl group bonded to a nitrogen atom, which is not represented by the formula CHO. Esters feature a carbonyl group bonded to an oxygen atom that is also attached to another carbon chain, thus differing in structure from aldehydes. Ethers, on the other hand, contain an oxygen atom bonded to two carbon atoms, which again does not align with the CHO structure.

Therefore, the formula CHO accurately portrays the structure of an aldehyde, making it the correct choice in this context.