Textbook Question
Using pKₐ values, calculate the equilibrium constants for the following acid–base reactions.
(b)
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3. Acids and Bases
Equilibrium Constant
1:50 minutesProblem 2
Textbook Question
Predict the Keq for the following acid–base reaction.
Verified step by step guidance1
Identify the acid and base on both sides of the reaction. Determine which species donates a proton (acid) and which species accepts a proton (base).
Determine the pKa values of the acids on both sides of the reaction. The pKa is a measure of the acid strength, with lower pKa values indicating stronger acids.
Use the relationship between pKa and Kₑq: \( K_{eq} = 10^{\Delta pKa} \), where \( \Delta pKa = pKa(\text{acid on the right}) - pKa(\text{acid on the left}) \).
Evaluate the \( \Delta pKa \) value to determine whether the equilibrium favors the reactants or the products. If \( \Delta pKa > 0 \), the equilibrium favors the products; if \( \Delta pKa < 0 \), the equilibrium favors the reactants.
Substitute the \( \Delta pKa \) value into the equation \( K_{eq} = 10^{\Delta pKa} \) to calculate the equilibrium constant qualitatively. This will give you an idea of the direction and extent of the reaction.
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Video duration:
1mKey Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Acid-Base Reactions
Acid-base reactions involve the transfer of protons (H⁺ ions) between reactants. In these reactions, acids donate protons while bases accept them. Understanding the nature of the acids and bases involved is crucial for predicting the outcome and equilibrium of the reaction.
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The Lewis definition of acids and bases.
Equilibrium Constant (Kₑq)
The equilibrium constant (Kₑq) quantifies the ratio of the concentrations of products to reactants at equilibrium for a given reaction. For acid-base reactions, Kₑq can be derived from the dissociation constants of the acids and bases involved, reflecting the strength of the acids and bases in the reaction.
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02:19The relationship between equilibrium constant and pKa.
Le Chatelier's Principle
Le Chatelier's Principle states that if a system at equilibrium is disturbed, the system will adjust to counteract the disturbance and restore a new equilibrium. This principle is essential for predicting how changes in concentration, pressure, or temperature will affect the Kₑq and the position of equilibrium in acid-base reactions.
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