Textbook Question
Which of the following bases can remove a proton from acetic acid in a reaction that favors products?
HO− CH3NH2 HC≡C− CH3OH H2O Cl−
3. Acids and Bases
Acid Base Equilibrium
3:49 minutesProblem 23a
Textbook Question
Given the Keq values for the following acid–base reactions, identify the strongest acid and the strongest base.
(a) 
Verified step by step guidance1
Step 1: Analyze the equilibrium constant (K_eq) provided in the reaction. A very large K_eq value, such as 1.0 × 10^20, indicates that the reaction strongly favors the products. This suggests that the acid and base on the reactant side are weaker compared to the conjugate acid and conjugate base on the product side.
Step 2: Identify the acid and base on both sides of the reaction. On the reactant side, hydrobromic acid (HBr) is the acid, and pyrrolidine is the base. On the product side, pyrrolidinium ion is the conjugate acid, and bromide ion is the conjugate base.
Step 3: Compare the strength of the acids. Hydrobromic acid (HBr) is a strong acid, as it completely dissociates in water. The pyrrolidinium ion, being the conjugate acid of pyrrolidine, is weaker than HBr because the equilibrium strongly favors its formation.
Step 4: Compare the strength of the bases. Pyrrolidine is a stronger base compared to the bromide ion because the equilibrium strongly favors the formation of pyrrolidinium ion and bromide ion, indicating that pyrrolidine readily accepts a proton.
Step 5: Conclude that the strongest acid in this reaction is hydrobromic acid (HBr), and the strongest base is pyrrolidine, based on the equilibrium constant and the nature of the species involved.
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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 balance between acids and bases in a chemical reaction. The equilibrium constant (K_eq) quantifies this balance, indicating the extent to which reactants are converted to products. A higher K_eq value suggests that the products are favored, which helps in determining the strength of acids and bases involved in the reaction.
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Strength of Acids and Bases
The strength of an acid or base is determined by its ability to donate protons (H+) or accept protons, respectively. Strong acids completely dissociate in solution, while weak acids do not. In the context of the given reaction, comparing K_eq values allows us to identify which species acts as the stronger acid or base based on their tendency to donate or accept protons.
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Conjugate Acid-Base Pairs
Conjugate acid-base pairs consist of an acid and its corresponding base that differ by a single proton. In the reaction provided, pyrrolidine and pyrrolidinium ion represent a conjugate pair, as do HBr and bromide ion. Understanding these pairs is crucial for determining the relative strengths of acids and bases, as the stronger acid will have a weaker conjugate base.
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