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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1:51 minutes

Problem 62h(iii, iv)

Textbook Question

For the following acid–base pairs, (iii) predict the favored side of equilibrium; (iv) calculate K_eq;
(h)

Verified step by step guidance

Step 1: Identify the acid and base on both sides of the equilibrium. In this reaction, NH₃ acts as a base and HCl acts as an acid. The products formed are NH₄⁺ (conjugate acid of NH₃) and Cl⁻ (conjugate base of HCl).

Step 2: Compare the relative strengths of the acids and bases involved. HCl is a strong acid, while NH₄⁺ is a weak acid. Similarly, NH₃ is a weak base, and Cl⁻ is a very weak base.

Step 3: Predict the favored side of the equilibrium. Since the reaction involves a strong acid (HCl) reacting with a weak base (NH₃), the equilibrium will favor the formation of the weaker acid and base, which are NH₄⁺ and Cl⁻.

Step 4: Use the pKa values to calculate the equilibrium constant (Keq). The relationship between Keq and pKa is given by the formula:

K_{eq} = 10^{(pKa}

_acid-pKa_{conjugate acid}). Look up the pKa values for HCl and NH₄⁺ to perform this calculation.

Step 5: Interpret the result. A large Keq value indicates that the equilibrium strongly favors the products (NH₄⁺ and Cl⁻), while a small Keq value would indicate that the reactants (NH₃ and HCl) are favored.

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Key Concepts

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

Acid-Base Equilibrium

Acid-base equilibrium refers to the state in which the rates of the forward and reverse reactions of an acid-base reaction are equal, resulting in constant concentrations of reactants and products. The position of equilibrium can be predicted based on the strength of the acids and bases involved, with stronger acids favoring the formation of weaker acids and vice versa.

Equilibrium Constant (K_eq)

The equilibrium constant (K_eq) quantifies the ratio of the concentrations of products to reactants at equilibrium for a given reaction at a specific temperature. A large K_eq value, such as 1.0 x 10^47, indicates that the products are favored at equilibrium, suggesting that the reaction proceeds almost to completion, while a small K_eq value would indicate that reactants are favored.

Strength of Acids and Bases

The strength of acids and bases is determined by their ability to donate or accept protons (H+ ions). Strong acids, like HBr, completely dissociate in solution, while weak acids do not. Similarly, strong bases readily accept protons, while weak bases do so less effectively. Understanding the relative strengths of the acids and bases involved is crucial for predicting the favored side of the equilibrium.

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Related Practice

Textbook Question

Indicate whether an alcohol (ROH) with a pK_a value of 15 has more charged or more neutral molecules in a solution with the pH values given in Problem 41.

3. pH = 7

4. pH = 10

5. pH = 13

Textbook Question

A naturally occurring amino acid such as alanine has a group that is a carboxylic acid and a group that is a protonated amine. The pK_a values of the two groups are shown.

d. Draw the structure of alanine in a solution at pH = 12.

Textbook Question

For the following acid–base reaction, (c) calculate the ratio of butan-2-ol to 2-butoxide.

Textbook Question

What percent of imidazole is protonated at physiological pH (7.4)?

Multiple Choice

Which of the following is a correct statement about the equilibrium constant (K) in a chemical reaction?

Multiple Choice

If a given acid/base reaction has a K_eq = 10²⁵, what does this mean about the stability of the molecules?

Multiple Choice

What is the approximate K_eq for the following acid/base reaction?

Multiple Choice