Question

Which of the following salts is the most basic in aqueous solution?
A. ${\text{FeC}}{{\text{l}}_{\text{3}}}$
B. ${\text{Pb}}{\left( {{\text{C}}{{\text{H}}_{\text{3}}}{\text{COO}}} \right)_{\text{2}}}$
C. ${\text{Al}}{\left( {{\text{CN}}} \right)_{\text{3}}}$
D. ${\text{C}}{{\text{H}}_{\text{3}}}{\text{COOK}}$

Answer 1

We know that the salts in their aqueous solution undergo hydrolysis. Hydrolysis is the reaction with water. The salts which form base on hydrolysis are more basic in aqueous solution.

Complete step by step answer:
We are given four salts ${\text{FeC}}{{\text{l}}_{\text{3}}}$, ${\text{Pb}}{\left( {{\text{C}}{{\text{H}}_{\text{3}}}{\text{COO}}} \right)_{\text{2}}}$, ${\text{Al}}{\left( {{\text{CN}}} \right)_{\text{3}}}$ and ${\text{C}}{{\text{H}}_{\text{3}}}{\text{COOK}}$.
Consider the hydrolysis of ${\text{FeC}}{{\text{l}}_{\text{3}}}$. ${\text{FeC}}{{\text{l}}_{\text{3}}}$ on hydrolysis produces iron (III) hydroxide and hydrochloric acid. The reaction is as follows:
${\text{FeC}}{{\text{l}}_{\text{3}}}\xrightarrow[{{\text{Hydrolysis}}}]{{{{\text{H}}_{\text{2}}}{\text{O}}}}{\text{Fe}}{\left( {{\text{OH}}} \right)_{\text{3}}} + {\text{HCl}}$
The hydrochloric acid produced during the hydrolysis of ${\text{FeC}}{{\text{l}}_{\text{3}}}$ is a strong acid and the iron (III) hydroxide is a weak base.
Consider the hydrolysis of ${\text{Pb}}{\left( {{\text{C}}{{\text{H}}_{\text{3}}}{\text{COO}}} \right)_{\text{2}}}$. ${\text{Pb}}{\left( {{\text{C}}{{\text{H}}_{\text{3}}}{\text{COO}}} \right)_{\text{2}}}$ on hydrolysis produces lead (II) hydroxide and acetic acid. The reaction is as follows:
${\text{Pb}}{\left( {{\text{C}}{{\text{H}}_{\text{3}}}{\text{COO}}} \right)_{\text{2}}}\xrightarrow[{{\text{Hydrolysis}}}]{{{{\text{H}}_{\text{2}}}{\text{O}}}}{\text{Pb}}{\left( {{\text{OH}}} \right)_{\text{2}}} + 2{\text{C}}{{\text{H}}_{\text{3}}}{\text{COOH}}$
The acetic acid produced during the hydrolysis of ${\text{Pb}}{\left( {{\text{C}}{{\text{H}}_{\text{3}}}{\text{COO}}} \right)_{\text{2}}}$ is a weak acid and the lead (II) hydroxide is a weak base.
Consider the hydrolysis of ${\text{Al}}{\left( {{\text{CN}}} \right)_{\text{3}}}$. ${\text{Al}}{\left( {{\text{CN}}} \right)_{\text{3}}}$ on hydrolysis produces aluminium hydroxide and hydrogen cyanide. The reaction is as follows:
${\text{Al}}{\left( {{\text{CN}}} \right)_{\text{3}}}\xrightarrow[{{\text{Hydrolysis}}}]{{{{\text{H}}_{\text{2}}}{\text{O}}}}{\text{Al}}{\left( {{\text{OH}}} \right)_{\text{3}}} + 3{\text{HCN}}$
The hydrogen cyanide produced during the hydrolysis of ${\text{Al}}{\left( {{\text{CN}}} \right)_{\text{3}}}$ is a strong acid and the aluminium hydroxide is a weak base.
Consider the hydrolysis of ${\text{C}}{{\text{H}}_{\text{3}}}{\text{COOK}}$. ${\text{C}}{{\text{H}}_{\text{3}}}{\text{COOK}}$ on hydrolysis produces potassium hydroxide and acetic acid. The reaction is as follows:
${\text{C}}{{\text{H}}_{\text{3}}}{\text{COOK}}\xrightarrow[{{\text{Hydrolysis}}}]{{{{\text{H}}_{\text{2}}}{\text{O}}}}{\text{KOH}} + {\text{C}}{{\text{H}}_{\text{3}}}{\text{COOH}}$
The acetic acid produced during the hydrolysis of ${\text{C}}{{\text{H}}_{\text{3}}}{\text{COOK}}$ is a weak acid and the potassium hydroxide is a strong base.
Thus, of all the bases formed, potassium hydroxide $\left( {{\text{KOH}}} \right)$ is a strong base.
Thus, the aqueous solution of ${\text{C}}{{\text{H}}_{\text{3}}}{\text{COOK}}$ is the most basic.

Therefore, the correct option is D. .

Note: The bases which dissociate completely are known as strong bases while the bases which do not dissociate completely are known as weak bases. Strong base gives a more basic solution.