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

Acid Base Equilibrium

Organic Chemistry

3. Acids and Bases

Acid Base Equilibrium

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Problem 62e(iii)

Textbook Question

For the following acid–base pairs, (iii) predict the favored side of equilibrium;
(e)

Verified step by step guidance

Identify the acid and base on both sides of the equilibrium. On the left side, the acid is ethanol (CH₃CH₂OH), and the base is the formate ion (HCOO⁻). On the right side, the conjugate acid is formic acid (HCOOH), and the conjugate base is the ethoxide ion (CH₃CH₂O⁻).

Determine the relative acidity of the acids on both sides of the equilibrium. Compare the pKa values: formic acid (HCOOH) has a pKa of approximately 3.75, while ethanol (CH₃CH₂OH) has a pKa of approximately 16. This indicates that formic acid is a much stronger acid than ethanol.

Analyze the stability of the conjugate bases. The formate ion (HCOO⁻) is resonance-stabilized, making it more stable than the ethoxide ion (CH₃CH₂O⁻), which lacks resonance stabilization.

Apply the principle that equilibrium favors the side with the weaker acid and the more stable conjugate base. Since formic acid is the stronger acid and the formate ion is the more stable conjugate base, the equilibrium will favor the left side.

Conclude that the favored side of the equilibrium is the side with ethanol (CH₃CH₂OH) and the formate ion (HCOO⁻), as this combination represents the weaker acid and the more stable conjugate base.

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Key Concepts

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

Acid-Base Theory

Acid-base theory explains the behavior of acids and bases in chemical reactions. According to the Brønsted-Lowry theory, acids are proton donors while bases are proton acceptors. Understanding this concept is crucial for predicting the direction of equilibrium in acid-base reactions, as the stronger acid will favor the formation of the weaker acid and the stronger base will favor the formation of the weaker base.

Equilibrium Constant (K)

The equilibrium constant (K) quantifies the ratio of the concentrations of products to reactants at equilibrium for a given reaction. A larger K value indicates that the products are favored at equilibrium, while a smaller K value suggests that the reactants are favored. This concept is essential for predicting the favored side of equilibrium in acid-base reactions, as it helps determine which side has a greater tendency to form.

pKa and pKb Values

pKa and pKb values are measures of the strength of acids and bases, respectively. The pKa value indicates the acidity of a compound, with lower values signifying stronger acids, while the pKb value indicates the basicity, with lower values signifying stronger bases. These values are critical for predicting the favored side of equilibrium, as they allow for comparison of the strengths of the acids and bases involved in the reaction.

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Related Practice

Textbook Question

The acid-catalyzed hydrolysis of an ester results in the formation of an equal amount of carboxylic acid and alcohol.

(a) Design a flow chart for separating the two products.

Textbook Question

Complete the following proposed acid–base reactions, and predict whether the reactants or products are favored.

(a)

(b)

Textbook Question

Show how you would use extractions with a separatory funnel to separate a mixture of the following compounds: benzoic acid, phenol, benzyl alcohol, aniline

Textbook Question

Phenols are less acidic than carboxylic acids, with values of pK_a around 10. Phenols are deprotonated by (and therefore soluble in) solutions of sodium hydroxide but not by solutions of sodium bicarbonate. Explain how you would use extractions to isolate the three pure compounds from a mixture of p-cresol (p-methylphenol), cyclohexanone, and benzoic acid.

Textbook Question

Ethyne (HC≡CH) has a pK_a value of 25, water has a pK_a value of 15.7, and ammonia (NH₃) has a pK_a value of 36. Draw the equation, showing equilibrium arrows that indicate whether reactants or products are favored, for the acid–base reaction of ethyne with

b. ⁻NH₂.

c. Which would be a better base to use if you wanted to remove a proton from ethyne, HO⁻ or ^-NH₂?

Textbook Question

For each of the acid–base reactions in [Section 2.3], compare the pK_a values of the acids on either side of the equilibrium arrows to prove that the equilibrium lies in the direction indicated.

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2. <IMAGE>

Textbook Question

For each of the acid–base reactions in [Section 2.3], compare the pK_avalues of the acids on either side of the equilibrium arrows to prove that the equilibrium lies in the direction indicated.

3. <IMAGE>

4. <IMAGE>

Textbook Question

Ethyne (HC≡CH) has a pK_a value of 25, water has a pK_a value of 15.7, and ammonia (NH3) has a pKa value of 36. Draw the equation, showing equilibrium arrows that indicate whether reactants or products are favored, for the acid–base reaction of ethyne with

a. HO^-.

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For the following acid–base pairs, (iii) predict the favored side of equilibrium;(e)

Key Concepts

Acid-Base Theory

Equilibrium Constant (K)

pKa and pKb Values

Watch next

For the following acid–base pairs, (iii) predict the favored side of equilibrium;
(e)