Question

What will be the decreasing order of basic strength of the following conjugate bases?
$\text{OH}^-, \, \text{R}^-, \, \text{CH}_3\text{COO}^-, \, \text{Cl}^-$

• A. $\text{Cl}^- > \text{OH}^- > \text{R}^- > \text{CH}_3\text{COO}^-$
• B. $\text{R}^- > \text{OH}^- > \text{CH}_3\text{COO}^- > \text{Cl}^-$
• C. $\text{OH}^- > \text{R}^- > \text{CH}_3\text{COO}^- > \text{Cl}^-$
• D. $\text{Cl}^- > \text{R}^- > \text{OH}^- > \text{CH}_3\text{COO}^-$

Answer 1

Answer: (B)

$\text{R}^- > \text{OH}^- > \text{CH}_3\text{COO}^- > \text{Cl}^-$

Answer 2

Understanding Basic Strength in Terms of Conjugate Acids:

The basic strength of a conjugate base is inversely related to the strength of its conjugate acid. A strong acid has a weak conjugate base, and a weak acid has a strong conjugate base.

Order of Acidity of Conjugate Acids:

To determine the basic strength of the conjugate bases, analyze the acidity of their conjugate acids:

• For $\text{OH}^-$: The conjugate acid is $\text{H}_2\text{O}$, which is a weak acid.
• For $\text{RO}^-$: The conjugate acid is $\text{R-OH}$ (an alcohol), which is generally weaker than water as an acid.
• For $\text{CH}_3\text{COO}^-$: The conjugate acid is $\text{CH}_3\text{COOH}$ (acetic acid), which is stronger than water and alcohols.
• For $\text{Cl}^-$: The conjugate acid is $\text{HCl}$, a strong acid.

Determine the Order of Basic Strength:

Based on the above analysis, the decreasing order of basic strength is:

$\text{RO}^- > \text{OH}^- > \text{CH}_3\text{COO}^- > \text{Cl}^-$

Conclusion:

The correct order of decreasing basic strength is:

$\text{RO}^- > \text{OH}^- > \text{CH}_3\text{COO}^- > \text{Cl}^-$

which corresponds to Option (2).