What will be the decreasing order of basic strength of the following conjugate bases?
\( \text{OH}^-, \, \text{R}^-, \, \text{CH}_3\text{COO}^-, \, \text{Cl}^- \)
\( \text{OH}^-, \, \text{R}^-, \, \text{CH}_3\text{COO}^-, \, \text{Cl}^- \)
- \( \text{Cl}^- > \text{OH}^- > \text{R}^- > \text{CH}_3\text{COO}^- \)
- \( \text{R}^- > \text{OH}^- > \text{CH}_3\text{COO}^- > \text{Cl}^- \)
- \( \text{OH}^- > \text{R}^- > \text{CH}_3\text{COO}^- > \text{Cl}^- \)
- \( \text{Cl}^- > \text{R}^- > \text{OH}^- > \text{CH}_3\text{COO}^- \)
The Correct Option is B
Approach Solution - 1
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).
Approach Solution -2
We are asked to find the decreasing order of basic strength of the following conjugate bases:
\( \text{OH}^-, \, \text{R}^-, \, \text{CH}_3\text{COO}^-, \, \text{Cl}^- \).
Here, \( \text{R}^- \) represents an alkyl group conjugate base, for example, \( \text{CH}_3^- \).
Step 2: Understanding basic strength of conjugate bases.
Basic strength of a conjugate base is related to the stability of the base and acidity of its conjugate acid. The weaker the acid, the stronger the conjugate base.
- \( \text{Cl}^- \) is the conjugate base of hydrochloric acid (HCl), which is a strong acid, making \( \text{Cl}^- \) a very weak base.
- \( \text{CH}_3\text{COO}^- \) is the conjugate base of acetic acid, a weak acid, so acetate ion has moderate basic strength.
- \( \text{OH}^- \) is the conjugate base of water, which is very weakly acidic, making hydroxide ion a relatively strong base.
- \( \text{R}^- \) (like \( \text{CH}_3^- \)) is the conjugate base of an alkane (\( \text{R-H} \)), which is an extremely weak acid. Therefore, the alkyl anion is a very strong base.
Step 3: Comparison of acidity of the parent acids.
Acidity order (from weakest acid to strongest):
\[ \text{R-H} < \text{H}_2\text{O} < \text{CH}_3\text{COOH} < \text{HCl} \] Corresponding conjugate bases have the opposite order in basic strength:
\[ \text{R}^- > \text{OH}^- > \text{CH}_3\text{COO}^- > \text{Cl}^- \]
Step 4: Reasoning based on stability.
- \( \text{Cl}^- \) is stabilized by resonance with the strong acid environment, so it's very weakly basic.
- \( \text{CH}_3\text{COO}^- \) has resonance stabilization which lowers its basicity.
- \( \text{OH}^- \) is less stabilized and hence more basic than acetate.
- \( \text{R}^- \) has a negative charge localized on carbon, no resonance stabilization, making it very unstable and hence a very strong base.
Step 5: Conclusion - Final order of basic strength.
Based on acidity, stability, and resonance effects, the decreasing order of base strength is:
\[ \boxed{ \text{R}^- > \text{OH}^- > \text{CH}_3\text{COO}^- > \text{Cl}^- } \] This means the alkyl anion is the strongest base, followed by hydroxide ion, acetate ion, and chloride ion.
Top JEE Main Chemistry Questions
What will be the equilibrium constant of the given reaction carried out in a \(5 \,L\) vessel and having equilibrium amounts of \(A_2\) and \(A\) as \(0.5\) mole and \(2 \times 10^{-6}\) mole respectively?
The reaction : \(A_2 \rightleftharpoons 2A\)- At equilibrium the concentrations of and in a sealed vessel at . What will be for the reaction
- Find out the major products from the following reactions
Cobalt chloride when dissolved in water forms pink colored complex $X$ which has octahedral geometry. This solution on treating with cone $HCl$ forms deep blue complex, $\underline{Y}$ which has a $\underline{Z}$ geometry $X, Y$ and $Z$, respectively, are
- The correct order of atomic radii is:
Top JEE Main Acid-base concepts and principles Questions
Top JEE Main Questions
- In a hydrogen like atom, when an electron jumps from the $M$ - shell to the $L$ - shell, the wavelength of emitted radiation is $\lambda$. If an electron jumps from $N$-shell to the $L$-shell, the wavelength of emitted radiation will be :
- Two masses $m$ and $\frac{m}{2}$ are connected at the two ends of a massless rigid rod of length $l$. The rod is suspended by a thin wire of torsional constant $k$ at the centre of mass of the rod-mass system(see figure). Because of torsional constant $k$, the restoring torque is $\tau =k\theta$ for angular displacement $\theta$. If the rod is rota ted by $\theta_0$ and released, the tension in it when it passes through its mean position will be:
What will be the equilibrium constant of the given reaction carried out in a \(5 \,L\) vessel and having equilibrium amounts of \(A_2\) and \(A\) as \(0.5\) mole and \(2 \times 10^{-6}\) mole respectively?
The reaction : \(A_2 \rightleftharpoons 2A\)- The value of is
- The number of terms of an is even. The sum of the odd terms is and of the even terms is . The last term exceeds the first by . Then the number of terms in the series is ______.