Question

The general formula of carboxylic acids is:
A. ${{C}_{n}}{{H}_{n}}COOH$
B. ${{C}_{n}}{{H}_{2n}}COOH$
C. ${{C}_{n}}{{H}_{n-2}}COOH$
D. ${{C}_{n}}{{H}_{2n+1}}COOH$

Answer 1

Hint: The general formula of the compounds is nothing but it represents the number of particular atoms present in the respective chemical. The general formula of alkanes is ${{C}_{n}}{{H}_{2n+2}}$ . Means in alkanes ‘n’ number of carbons and ‘2n+2’ number of hydrogens are present.

Complete answer:
- In the question it is given that the general formula of carboxylic acid is.
- We have to find which option is correct for the general formula of carboxylic acid.
- Carboxylic acid is one of the functional groups and which can be represented as –COOH.
- For every organic molecule there is a general formula to represent the number of carbon atoms, hydrogen atoms and oxygen atoms present in it.
- Carboxylic acid also has a general formula and it is ${{C}_{n}}{{H}_{2n+1}}COOH$ .
- Means in carboxylic acids if it contains an ‘n’ number of carbons then it will have n+1 hydrogens other than the functional group –COOH.
- Therefore the general formula of carboxylic acid is ${{C}_{n}}{{H}_{2n+1}}COOH$.

- So, the correct option is D.

Note: Take an example of acetic acid. The molecular formula of acetic acid is $C{{H}_{3}}COOH$ . Now compare the molecular formula of acetic with the general formula of acetic acid.
If we take n = 1in${{C}_{n}}{{H}_{2n+1}}COOH$, then we will get $C{{H}_{3}}COOH$ (ethanoic acid).
If we take n = 2 in ${{C}_{n}}{{H}_{2n+1}}COOH$ , then we will get ${{C}_{2}}{{H}_{5}}COOH$ (propionic acid).
If we take n = 3 in ${{C}_{n}}{{H}_{2n+1}}COOH$ , then we will get ${{C}_{3}}{{H}_{7}}COOH$ (butanoic acid).