Question

Which of the following salts will give highest $pH$ in water?

• A. $KCl$
• B. $NaCl$
• C. $Na_2CO_3$
• D. $CuSO_4$

Answer 1

Answer: (C)

$Na_2CO_3$

Answer 2

The highest $pH$ refers to the basic solution containing $OH^-$ " ions. Therefore, the basic salt releasing more $OH^-$ ions on hydrolysis will give highest $pH$ in water.
Only the salt of strong base and weak acid would release more $OH^-$ ion on hydrolysis. Among the given salts, $Na_2CO_3$ corresponds to the basic salt as it is formed by the neutralisation of $NaOH$ [strong base] and $H_2CO_3$ [weak acid].
$\, \, \, \, \, \, \, CO_3^{2-} + H_2O \rightleftharpoons HCO_3^- + OH^-$