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

Acids and Bases

Organic Chemistry

3. Acids and Bases

Acids and Bases

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Multiple Choice

Which of the following is the correct expression for the acid dissociation constant (Ka) of a weak acid HA in water?

Ka = [H+][HA]/[A-]

Ka = [HA]/[H+][A-]

Ka = [H+][A-]/[HA]

Ka = [A-]/[H+][HA]

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Verified step by step guidance

Understand the concept of acid dissociation constant (Ka): It is a measure of the strength of an acid in solution, specifically how well an acid dissociates into its ions in water.

Write the general dissociation equation for a weak acid HA in water: HA ⇌ H⁺ + A⁻.

According to the law of mass action, the equilibrium expression for this dissociation is given by the concentration of the products over the concentration of the reactants.

Set up the expression for Ka: Ka = ([H⁺][A⁻]) / [HA]. This expression shows that Ka is the product of the concentrations of the dissociated ions divided by the concentration of the undissociated acid.

Verify the expression: Compare the given options with the derived expression to identify the correct one, which is Ka = [H⁺][A⁻]/[HA].