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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2:41 minutes

Problem 46c

Textbook Question

Given the pK_b, calculate the pK_a of the conjugate acid.
(c)

Verified step by step guidance

Step 1: Recall the relationship between pKa and pKb for a conjugate acid-base pair. The equation is: \( pKa + pKb = 14 \). This equation is derived from the ionization constant of water \( K_w \), where \( K_w = 10^{-14} \) at 25°C.

Step 2: Identify the given value in the problem. The pKb of morpholine is provided as \( 5.6 \). This corresponds to the basicity of morpholine.

Step 3: Rearrange the equation \( pKa + pKb = 14 \) to solve for pKa. The rearranged equation is: \( pKa = 14 - pKb \).

Step 4: Substitute the given pKb value into the rearranged equation. Replace \( pKb \) with \( 5.6 \) in the equation \( pKa = 14 - pKb \).

Step 5: Perform the subtraction to calculate the pKa value. The result will represent the acidity of the conjugate acid of morpholine.

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Key Concepts

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

pKa and pKb Relationship

The pKa and pKb values are related through the equation pKa + pKb = 14 at 25°C. The pKa represents the acidity of a compound, while pKb indicates its basicity. For a conjugate acid-base pair, knowing one value allows the calculation of the other, which is essential for understanding the strength of acids and bases.

Conjugate Acids and Bases

A conjugate acid is formed when a base accepts a proton (H+), while a conjugate base is what remains after an acid donates a proton. In this context, morpholine acts as a base, and its conjugate acid is formed when it accepts a proton. Understanding this relationship is crucial for calculating pKa from pKb.

Morpholine Structure and Properties

Morpholine is a cyclic amine with a nitrogen atom in its structure, which contributes to its basic properties. The presence of the nitrogen atom allows morpholine to accept protons, making it a base. Its pKb value of 5.6 indicates its strength as a base, which is important for determining the pKa of its conjugate acid.