Question

The general formula of Carboxylic acid is:
a.) \[{C_n}{H_n}COOH\]
b.) \[{C_n}{H_{2n}}COOH\]
c.) \[{C_n}{H_{2n - 2}}COOH\]
d.) \[{C_n}{H_{2n + 1}}COOH\]

Answer 1

Hint: Before answering this question, let us recall what carboxylic acids are. They are actually a class of organic compounds in which a carbon (C) atom is bonded to an oxygen (O) atom by a double bond and to a hydroxyl group (―OH) by a single bond. Another bond links the carbon atom to a hydrogen (H) atom or to some other monovalent combining group.

Complete step by step answer:
An interesting fact is that Carboxylic acid is named because of the presence of carboxyl (C=O) group and the hydroxyl (-OH) group. They are usually more acidic than other organic compounds containing hydroxyl groups but are weaker than the mineral acids like hydrochloric acid and sulphuric acid.
Carboxylic acids are derivatives of hydrocarbons in which one or more of the hydrogen atoms in the hydrocarbon have been replaced by a carboxyl group. The first four carboxylic acids derived from alkanes are methanoic acid, ethanoic acid, propanoic acid and butanoic acid.
Acids with less than about five carbons are soluble in water while those with a higher molecular weight are insoluble due to the larger hydrocarbon portion, which is hydrophobic.
The general molecular formula is \[{C_n}{H_{2n + 1}}COOH\]
Hence, the correct answer is Option (D) \[{C_n}{H_{2n + 1}}COOH\]

Note:
Carboxylic acids and Esters are functional group isomers. That means even though they have the exact same molecular formula, their bond connectivity is different. By seeing only the molecular formula we would not be able to decide if a compound is a carboxylic acid. We would also have to look at its structural formula.