Question

Which of the following aqueous solution of salt have \(pH < 7\) at \(298\) K?

• A. \(\text{KNO}_3\)
• B. \(\text{Na}_2\text{CO}_3\)
• C. \(\text{CH}_3\text{COONH}_4\)
• D. \(\text{CuCl}_2\)

Hint:

A salt of a strong acid and a weak base gives an acidic solution.

Answer 1

The Correct Option is D

Step 1: Look for the cation or anion that reacts with water
K$^+$ and Cl$^-$ and NO$_3^-$ do not react. CO$_3^{2-}$ takes H$^+$, leaving OH$^-$. Cu$^{2+}$ is a small, highly charged ion that releases H$^+$ from water.

Step 2: Result
Only CuCl$_2$ gives an acidic solution, option (D).

Final Answer:
Option (D). \[ \boxed{\text{(D)}} \]