Question

Why $HF$ is a weak acid while $HCl$ is a strong acid?

• A. $HF$ produces very few $H^{+}$ ions in water
• B. $HCl$ dissociates completely to produce many $H^{+}$ ions in water
• C. Both $A$ and $B$
  
• D. None of the above

Answer 1

Answer: (C)

Both $A$ and $B$

Acids which ionises completely into its ions are called strong acids. A strong acid is one which is virtually 100% ionised in solution. $HCl$ dissociates completely to produce many $H^{+}$ ions in water whereas $HF$ produces very few $H^{+}$ ions in water due to the lesser stability of $F^{-}$ as compared to $C{l}^{-}$. Hence, $HF$ is a weak acid while $HCl$ is a strong acid.