Textbook Question
Give the products of the following acid–base reactions and indicate whether reactants or products are favored at equilibrium.
a.
3. Acids and Bases
Acid Base Equilibrium
4:21 minutesProblem 22c
Textbook Question
Given the value of Keq for the following acid–base reactions, identify the weakest acid and the weakest base.
(c) 
Verified step by step guidance1
Step 1: Analyze the equilibrium constant (K_eq) value provided in the reaction. A high K_eq value (7.9 × 10³) indicates that the reaction strongly favors the products over the reactants.
Step 2: Identify the acids and bases in the reaction. Ethanol (CH₃CH₂OH) acts as the acid in the reactants, and hydrochloric acid (HCl) is the stronger acid. In the products, ethyloxonium ion (CH₃CH₂OH₂⁺) is the conjugate acid, and chloride ion (Cl⁻) is the conjugate base.
Step 3: Compare the relative strengths of the acids. Since the reaction favors the formation of ethyloxonium ion (CH₃CH₂OH₂⁺) and chloride ion (Cl⁻), hydrochloric acid (HCl) is the stronger acid, making ethanol (CH₃CH₂OH) the weaker acid.
Step 4: Compare the relative strengths of the bases. Chloride ion (Cl⁻) is the conjugate base of hydrochloric acid, which is a strong acid. Strong acids have weak conjugate bases, so Cl⁻ is the weaker base compared to ethanol (CH₃CH₂OH).
Step 5: Conclude that the weakest acid in the reaction is ethanol (CH₃CH₂OH), and the weakest base is chloride ion (Cl⁻).
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Acid-Base Equilibrium
Acid-base equilibrium refers to the state where the rates of the forward and reverse reactions in an acid-base reaction are equal, resulting in constant concentrations of reactants and products. The equilibrium constant (K_eq) quantifies this balance, indicating the strength of the acids and bases involved. A higher K_eq value suggests a stronger acid and a weaker base, while a lower K_eq indicates the opposite.
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Strength of Acids and Bases
The strength of an acid or base is determined by its ability to donate or accept protons (H+ ions). Strong acids, like hydrochloric acid (HCl), dissociate completely in solution, while weak acids, such as ethanol, do not. In the context of the given reaction, the weakest acid is the one that is less likely to donate a proton, and the weakest base is the one that is less likely to accept a proton.
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Conjugate Acid-Base Pairs
In acid-base reactions, acids and bases exist as conjugate pairs. When an acid donates a proton, it forms its conjugate base, and when a base accepts a proton, it forms its conjugate acid. Understanding these pairs is crucial for identifying the weakest acid and base in a reaction. In the provided reaction, the ethyl oxonium ion is the conjugate acid of ethanol, while the chloride ion is the conjugate base of hydrochloric acid.
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