Question

The molecular formula ${C_4}{H_8}{O_2}$ represents.
A) An acid only.
B) An ester only.
C) A ketone only.
D) An acid and an ester also.

Answer 1

We see about the functional group.
Functional group:
The functional group is an atom or a group of atoms that determine the characteristic property of the organic compounds despite the size of the molecule members of the same functional group undergo the identical chemical reaction.

Complete step by step answer:

Let us see the functional group in detail.
A functional group may be a specific group of atoms or bonds with a compound that is liable for the characteristic chemical reactions of that compound and the molecules with the same functional group undergo similar reactions. The functional group is more important to name the organic compound.
Now, we see an aldehyde functional group.
An organic compound that contains a carbonyl group with the central carbon atom bonded to the alkyl group is called Ketone. Hence option C is incorrect.
The structure of ester,

An ester is recognized by the position and bonding of the atoms, where R and R’ are both carbon-initiated chains of varying length, also known as alkyl groups. Hence option B is incorrect.
The molecular formula ${C_4}{H_8}{O_2}$ represents an acid (Butyric acid) and an ester compound (ethyl acetate). Therefore, the option D is correct.
Ethyl acetate is a compound which has a molecular formula as ${C_4}{H_8}{O_2}$.
The structure of ethyl acetate is given below,

Butyric acid is a compound which has a molecular formula as ${C_4}{H_8}{O_2}$.
The structure of butyric acid is given below,

Therefore, the option D is correct.

Note:
We must remember that an organic compound may contain more than one functional group. To classify the functional group one must know their formula.
Example: The formula for the hydroxyl functional group is $- OH$ and the functional group for the acidic group is $- COOH$.