Problem 17
Question
State which of the following ions or compounds has the strongest conjugate base and briefly explain your choice. (a) \(\mathrm{HSO}_{4}^{-}\) (b) \(\mathrm{CH}_{3} \mathrm{CO}_{2} \mathrm{H}\) (c) HClO
Step-by-Step Solution
Verified Answer
The strongest conjugate base is \( \mathrm{ClO}^- \), from \( \mathrm{HClO} \).
1Step 1: Understand the Concept of Conjugate Bases
A conjugate base is what remains after an acid donates a proton (H⁺). The strength of a conjugate base is inversely related to the strength of its acid. The weaker the acid, the stronger its conjugate base will be.
2Step 2: Identify the Parent Acids
Determine the parent acids for each given ion or compound.- \( \mathrm{HSO}_4^{-} \) is the conjugate base of \( \mathrm{H}_2\mathrm{SO}_4 \) (sulfuric acid).- \( \mathrm{CH}_3 \mathrm{CO}_2 \mathrm{H} \) is acetic acid, so its conjugate base would be \( \mathrm{CH}_3 \mathrm{CO}_2^- \).- \( \mathrm{HClO} \) is hypochlorous acid, so its conjugate base is \( \mathrm{ClO}^- \).
3Step 3: Assess the Acid Strengths
Identify the relative strengths of the parent acids:- \( \mathrm{H}_2\mathrm{SO}_4 \) is a strong acid, meaning it dissociates completely in solution.- \( \mathrm{CH}_3 \mathrm{CO}_2 \mathrm{H} \) is a weak acid.- \( \mathrm{HClO} \) is also a weak acid, but weaker than \( \mathrm{CH}_3 \mathrm{CO}_2 \mathrm{H} \).
4Step 4: Determine the Strongest Conjugate Base
Since \( \mathrm{HClO} \) is the weakest acid among the options, its conjugate base \( \mathrm{ClO}^- \) will be the strongest of the conjugate bases provided.
Key Concepts
Acid StrengthWeak AcidsConjugate Acid-Base Pairs
Acid Strength
Understanding acid strength is crucial when exploring conjugate bases. Acid strength refers to an acid's ability to donate a proton (
H⁺
). Strong acids dissociate completely in water, releasing all their protons. For example, sulfuric acid (
H_2SO_4
) is a strong acid. It fully dissociates in solution, meaning it is highly effective at donating protons.
In contrast, weak acids do not fully dissociate. They release fewer protons, demonstrating a lower tendency to give up their hydrogen ions. Understanding the strength of an acid helps to predict the strength of its conjugate base. Strong acids produce weak conjugate bases, and weak acids produce stronger conjugate bases. This inverse relationship is key in predicting and comparing conjugate base strengths.
In contrast, weak acids do not fully dissociate. They release fewer protons, demonstrating a lower tendency to give up their hydrogen ions. Understanding the strength of an acid helps to predict the strength of its conjugate base. Strong acids produce weak conjugate bases, and weak acids produce stronger conjugate bases. This inverse relationship is key in predicting and comparing conjugate base strengths.
Weak Acids
Weak acids only partially dissociate in water, which means they release some, but not all, of their hydrogen ions. Because they don't fully give up their protons, their conjugate bases are stronger than those of strong acids.
Examples of weak acids include acetic acid ( CH_3CO_2H ) and hypochlorous acid ( HClO ). Between these two, hypochlorous acid is even weaker than acetic acid. This lower dissociation ability results in a stronger conjugate base. The weak nature of HClO , for instance, makes its conjugate base, ClO^- , relatively strong, which is an important feature in acid-base chemistry.
Examples of weak acids include acetic acid ( CH_3CO_2H ) and hypochlorous acid ( HClO ). Between these two, hypochlorous acid is even weaker than acetic acid. This lower dissociation ability results in a stronger conjugate base. The weak nature of HClO , for instance, makes its conjugate base, ClO^- , relatively strong, which is an important feature in acid-base chemistry.
Conjugate Acid-Base Pairs
In any acid-base reaction, there are always conjugate acid-base pairs involved. A conjugate base is the species that remains after an acid has donated a proton. Conversely, a conjugate acid is formed when a base accepts a proton.
Take sulfuric acid ( H_2SO_4 ), for example. After losing a proton, it transforms into its conjugate base, HSO_4^- . Since H_2SO_4 is a strong acid, HSO_4^- is a weak conjugate base. In general, when comparing conjugate bases, the weaker the parent acid, the stronger the conjugate base. This principle helps identify that ClO^- , derived from the weakest acid amongst the choices, HClO , is the strongest conjugate base in this scenario.
Take sulfuric acid ( H_2SO_4 ), for example. After losing a proton, it transforms into its conjugate base, HSO_4^- . Since H_2SO_4 is a strong acid, HSO_4^- is a weak conjugate base. In general, when comparing conjugate bases, the weaker the parent acid, the stronger the conjugate base. This principle helps identify that ClO^- , derived from the weakest acid amongst the choices, HClO , is the strongest conjugate base in this scenario.
Other exercises in this chapter
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