91Ó°ÊÓ

The following equilibrium is established when hydrogen chloride is dissolved in acetic acid. \(\mathrm{HCl}+\mathrm{CH}_{3} \mathrm{COOH} \leftrightarrow \mathrm{Cl}^{-}+\mathrm{CH}_{3} \mathrm{COOH}_{2}^{+}\) The set that characterizes the conjugate acid base pair is (a) \(\left(\mathrm{HCl}, \mathrm{CH}_{3} \mathrm{COOH}\right)\) and \(\left(\mathrm{CH}_{3} \mathrm{COOH}_{2}^{+}, \mathrm{Cl}^{-}\right)\) (b) \(\left(\mathrm{HCl}, \mathrm{CH}_{3} \mathrm{COOH}_{2}^{+}\right)\)and \(\left(\mathrm{HCl}, \mathrm{CH}_{3} \mathrm{COOH}_{2}^{+}\right)\)and \(\left(\mathrm{CH}_{3} \mathrm{COOH}, \mathrm{Cl}^{-}\right)\) (c) \(\left(\mathrm{CH}_{3} \mathrm{COOH}_{2}^{+}, \mathrm{HCl}\right)\) and \(\left(\mathrm{Cl}^{-}, \mathrm{CH}_{3} \mathrm{COOH}\right)\) (d) \(\left(\mathrm{HCl}, \mathrm{Cl}^{-}\right)\)and \(\left(\mathrm{CH}_{3} \mathrm{COOH}_{2}^{+}, \mathrm{CH}_{3} \mathrm{COOH}\right)\)

Step by step solution

01

Identify the Possible Conjugate Pairs

In a chemical equilibrium involving an acid, there is a conjugate base, and likewise, with a base, there is a conjugate acid. In the given reaction: \( \mathrm{HCl} + \mathrm{CH}_{3} \mathrm{COOH} \leftrightarrow \mathrm{Cl}^{-} + \mathrm{CH}_{3} \mathrm{COOH}_{2}^{+} \), we need to identify which pairs are conjugate acid-base pairs.

02

Evaluate Each Compound's Role

Starting with \( \mathrm{HCl} \), it donates a proton to become \( \mathrm{Cl}^{-} \), making \( \mathrm{HCl} \) the acid and \( \mathrm{Cl}^{-} \) its conjugate base. The compound \( \mathrm{CH}_{3} \mathrm{COOH} \) accepts a proton to become \( \mathrm{CH}_{3} \mathrm{COOH}_{2}^{+} \), thus \( \mathrm{CH}_{3} \mathrm{COOH} \) is the base and \( \mathrm{CH}_{3} \mathrm{COOH}_{2}^{+} \) is its conjugate acid.

03

Match Pairs to Options

Based on the identification: \( (\mathrm{HCl}, \mathrm{Cl}^{-}) \) and \( (\mathrm{CH}_{3} \mathrm{COOH}_{2}^{+}, \mathrm{CH}_{3} \mathrm{COOH}) \) are the conjugate pairs in the given equilibrium. Look through the options provided to find the set that matches these identified conjugate pairs.

04

Select the Correct Answer

Option (d) provides the conjugate acid-base pairs as \( (\mathrm{HCl}, \mathrm{Cl}^{-}) \) and \( (\mathrm{CH}_{3} \mathrm{COOH}_{2}^{+}, \mathrm{CH}_{3} \mathrm{COOH}) \), which match the pairs we identified as conjugate pairs in the equilibrium.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Acid-Base Equilibrium

In chemical reactions, acid-base equilibrium is a dynamic state where acids and bases react with each other until they reach a balance in which the forward and reverse reactions occur at the same rate. In the example of hydrogen chloride dissolved in acetic acid, we observe this equilibrium as the system adjusts the concentrations of reactants and products. Here, hydrochloric acid (HCl) donates a proton to acetic acid (\(\mathrm{CH}_3\mathrm{COOH}\)). As a result, equilibrium is established between HCl and CH\(_3\)COOH and their respective ions, Cl\(^-\) and CH\(_3\)COOH\(_2^+\).

• In equilibrium, no net change in the concentration of reactants and products is observed because their rates of formation are equal.
• The concept of equilibrium allows us to predict the direction of a reaction and its position at any given point.

Understanding acid-base equilibrium is essential for predicting the behavior of acids and bases in a reaction.

Proton Transfer

Proton transfer is the fundamental process in acid-base reactions where a proton (H\(^+\)) is shifted from one molecule to another. In the example provided, HCl acts as a proton donor, releasing its proton to acetic acid. This transfer forms Cl\(^-\) and CH\(_3\)COOH\(_2^+\).

• Proton donors are classified as acids, while proton acceptors are named bases.
• The efficiency of proton transfer can influence the strength of an acid or a base.

Proton transfer is crucial because it leads to the formation of conjugate acid-base pairs, which achieve equilibrium in reactions involving acids and bases.

Chemical Equilibrium

Chemical equilibrium refers to the state when the rate of the forward reaction equals the rate of the reverse reaction. It is a key concept in understanding how conjugate acid-base pairs reach a stable state in solutions. In the provided equation, the equilibrium between HCl and CH\(_3\)COOH and their respective ions, Cl\(^-\) and CH\(_3\)COOH\(_2^+\), demonstrates this balance.

• At equilibrium, the concentrations of reactants and products remain constant.
• The system maintains the equilibrium even if the reaction does not stop; it simply occurs at equal rates in both directions.

This balance implies that the reaction can proceed in either direction depending on the initial conditions and can be influenced by factors like concentration, temperature, and pressure.

Acids and Bases in Organic Chemistry

In organic chemistry, acids and bases play crucial roles in numerous reactions, often facilitating changes in the structure and reactivity of organic molecules. Acetic acid and hydrochloric acid presented in the problem are excellent examples of organic and inorganic acids, respectively.

• Acetic acid (\(\mathrm{CH}_3\mathrm{COOH}\)) is a typical example of an organic acid, commonly found in vinegar.
• It acts as a proton acceptor in reactions, showcasing its ability to participate in equilibrium with other acids or bases.
• Acids in organic chemistry can influence reaction pathways, alter stereochemistry, and affect reaction rates.

Understanding the behavior of acids and bases in organic chemistry is essential for advanced studies in chemistry, as it allows chemists to manipulate and predict reactions outcomes effectively.