Q1 / 150 · MHT CET 2026 (18 April Shift 2) · Chemistry
Which of the following aqueous salt solutions has the least pH value ?
- A$\text{Na}_2\text{CO}_3$
- Correct answerB$\text{CuCl}_2$
- C$\text{CH}_3\text{COONa}$
- D$\text{NaNO}_3$
Solution
$\text{Na}_2\text{CO}_3$ is a salt of a strong base ($\text{NaOH}$) and a weak acid ($\text{H}_2\text{CO}_3$), so its aqueous solution is basic with $\text{pH} > 7$.
$\text{CuCl}_2$ is a salt of a weak base ($\text{Cu(OH)}_2$) and a strong acid ($\text{HCl}$), so its aqueous solution undergoes cationic hydrolysis to give an acidic solution with $\text{pH} < 7$.
$\text{CH}_3\text{COONa}$ is a salt of a strong base ($\text{NaOH}$) and a weak acid ($\text{CH}_3\text{COOH}$), so its aqueous solution is basic with $\text{pH} > 7$.
$\text{NaNO}_3$ is a salt of a strong base ($\text{NaOH}$) and a strong acid ($\text{HNO}_3$), so its aqueous solution is neutral with $\text{pH} = 7$.
Therefore, $\text{CuCl}_2$ has the least pH value.
Answer: $\text{CuCl}_2$
$\text{CuCl}_2$ is a salt of a weak base ($\text{Cu(OH)}_2$) and a strong acid ($\text{HCl}$), so its aqueous solution undergoes cationic hydrolysis to give an acidic solution with $\text{pH} < 7$.
$\text{CH}_3\text{COONa}$ is a salt of a strong base ($\text{NaOH}$) and a weak acid ($\text{CH}_3\text{COOH}$), so its aqueous solution is basic with $\text{pH} > 7$.
$\text{NaNO}_3$ is a salt of a strong base ($\text{NaOH}$) and a strong acid ($\text{HNO}_3$), so its aqueous solution is neutral with $\text{pH} = 7$.
Therefore, $\text{CuCl}_2$ has the least pH value.
Answer: $\text{CuCl}_2$
Hence, the correct answer is option: 'B'.