Table of contents

1. A Review of General Chemistry5h 5m
2. Molecular Representations1h 14m
3. Acids and Bases2h 46m
4. Alkanes and Cycloalkanes4h 17m
5. Chirality3h 39m
6. Thermodynamics and Kinetics1h 22m
7. Substitution Reactions1h 48m
8. Elimination Reactions2h 30m
9. Alkenes and Alkynes2h 9m
10. Addition Reactions3h 19m
11. Radical Reactions1h 58m
12. Alcohols, Ethers, Epoxides and Thiols2h 42m
13. Alcohols and Carbonyl Compounds2h 17m
14. Synthetic Techniques1h 26m
15. Analytical Techniques:IR, NMR, Mass Spect7h 3m
16. Conjugated Systems6h 13m
17. Ultraviolet Spectroscopy51m
18. Aromaticity2h 34m
19. Reactions of Aromatics: EAS and Beyond5h 1m
20. Phenols55m
21. Aldehydes and Ketones: Nucleophilic Addition4h 56m
22. Carboxylic Acid Derivatives: NAS2h 51m
23. The Chemistry of Thioesters, Phophate Ester and Phosphate Anhydrides1h 10m
24. Enolate Chemistry: Reactions at the Alpha-Carbon1h 53m
25. Condensation Chemistry2h 9m
26. Amines1h 43m
27. Heterocycles2h 0m
28. Carbohydrates5h 53m
29. Amino Acids4h 20m
30. Peptides and Proteins2h 42m
31. Catalysis in Organic Reactions1h 30m
32. Lipids 2h 50m
33. The Organic Chemistry of Metabolic Pathways2h 52m
34. Nucleic Acids1h 32m
35. Transition Metals6h 14m
36. Synthetic Polymers1h 49m

3. Acids and Bases

Equilibrium Constant

Organic Chemistry

3. Acids and Bases

Equilibrium Constant

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4:38 minutes

Problem 2b

Textbook Question

Using pKₐ values, calculate the equilibrium constants for the following acid–base reactions.
(b)

Verified step by step guidance

Identify the acids and bases in the reaction. Determine which species is the acid and which is the conjugate acid, as well as the base and its conjugate base.

Write the general relationship between the equilibrium constant (K_eq) and the pKₐ values of the acids involved in the reaction. The formula is:

K

_eq = 10^{(pKₐ (acid on reactant side) - pKₐ (acid on product side))}.

Look up the pKₐ values for the acids on both the reactant and product sides of the reaction. These values are typically found in a pKₐ table.

Substitute the pKₐ values into the formula from step 2. Ensure that the correct pKₐ values are used for the acid on the reactant side and the acid on the product side.

Simplify the expression to calculate the equilibrium constant (K_eq). This will give you the ratio of the concentrations of products to reactants at equilibrium.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

pKₐ and its significance

pKₐ is a measure of the strength of an acid in solution, defined as the negative logarithm of the acid dissociation constant (Kₐ). A lower pKₐ value indicates a stronger acid, as it dissociates more completely in water. Understanding pKₐ values is essential for predicting the direction of acid-base reactions and calculating equilibrium constants.

Equilibrium constant (K)

The equilibrium constant (K) quantifies the ratio of the concentrations of products to reactants at equilibrium for a given reaction. For acid-base reactions, K can be derived from the pKₐ values of the acids and bases involved. This relationship allows chemists to determine the extent to which a reaction favors products or reactants under specific conditions.

Henderson-Hasselbalch equation

The Henderson-Hasselbalch equation relates pH, pKₐ, and the ratio of the concentrations of the deprotonated and protonated forms of a weak acid or base. It is useful for calculating the pH of buffer solutions and understanding how changes in pKₐ affect the equilibrium position of acid-base reactions. This equation is fundamental in predicting the behavior of acids and bases in biological and chemical systems.

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