Question

The strongest acid among the following is:

• A. Salicylic acid
• B. \( m \)-hydroxybenzoic acid
• C. \( p \)-hydroxybenzoic acid
• D. Benzoic acid

Hint:

The strength of an acid is influenced by the stability of its conjugate base. Substituents that can stabilize the conjugate base, such as through hydrogen bonding or electron withdrawing effects, increase the acid strength.

Answer 1

The Correct Option is A

Step 1: Understanding Acid Strength 
The strength of an acid depends on the stability of its conjugate base. The more stable the conjugate base, the stronger the acid. 
Step 2: Analyzing the Compounds 
Salicylic acid: Contains both a carboxylic acid group and a hydroxyl group at the ortho position. The ortho hydroxyl group can form intramolecular hydrogen bonding with the carboxylate anion, stabilizing the conjugate base. 
\( m \)-hydroxybenzoic acid: The hydroxyl group is at the meta position, which does not significantly stabilize the carboxylate anion. 
\( p \)-hydroxybenzoic acid: The hydroxyl group is at the para position, which also does not significantly stabilize the carboxylate anion. 
Benzoic acid: Lacks any additional substituents that could stabilize the conjugate base. 
Step 3: Determining the Strongest Acid 
Salicylic acid is the strongest acid because the ortho hydroxyl group stabilizes the conjugate base through intramolecular hydrogen bonding, making it easier to lose a proton. 
Step 4: Matching with the Options 
The strongest acid is salicylic acid, which corresponds to option (A). 

Final Answer: The strongest acid is (A) Salicylic acid.