Question

Which one of the following is the weakest acid?

• A. HF
• B. HCl
• C. HBr
• D. HI

Hint:

Acid strength of HX increases down the group as bond strength decreases.

Answer 1

The Correct Option is A

Understanding the Concept: Acid strength in hydrogen halides increases down the group due to decrease in bond strength.

Step 1: Bond strength order: \[ HF>HCl>HBr>HI \]

Step 2: Reason: Stronger bond → harder to release H$^+$ → weaker acid.

Step 3: HF has strongest H–F bond. Final Answer:
Thus, HF is the weakest acid.