Table of contents

1. Intro to General Chemistry3h 48m
2. Atoms & Elements4h 16m
3. Chemical Reactions4h 10m
4. BONUS: Lab Techniques and Procedures1h 38m
5. BONUS: Mathematical Operations and Functions48m
6. Chemical Quantities & Aqueous Reactions3h 53m
7. Gases3h 49m
8. Thermochemistry2h 37m
9. Quantum Mechanics2h 58m
10. Periodic Properties of the Elements3h 9m
11. Bonding & Molecular Structure3h 29m
12. Molecular Shapes & Valence Bond Theory1h 57m
13. Liquids, Solids & Intermolecular Forces2h 23m
14. Solutions3h 1m
15. Chemical Kinetics2h 53m
16. Chemical Equilibrium2h 29m
17. Acid and Base Equilibrium5h 1m
18. Aqueous Equilibrium4h 47m
19. Chemical Thermodynamics1h 50m
20. Electrochemistry2h 42m
21. Nuclear Chemistry2h 36m
22. Organic Chemistry5h 7m
23. Chemistry of the Nonmetals2h 39m
24. Transition Metals and Coordination Compounds3h 16m

17. Acid and Base Equilibrium

pH of Strong Acids and Bases

General Chemistry

17. Acid and Base Equilibrium

pH of Strong Acids and Bases

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Multiple Choice

Pyridinium bromide (C5H5NHBr) is a strong electrolyte that dissociates completely into C5H5NH+ and Br-. A solution of pyridinium bromide has a pH of 2.92. Kb for pyridine is 1.7×10^-9. What is the molarity of the solution?

0.10 M

1.0 M

0.001 M

0.01 M

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Verified step by step guidance

Start by understanding that pyridinium bromide (C5H5NHBr) dissociates completely in water into pyridinium ion (C5H5NH+) and bromide ion (Br-). Since it is a strong electrolyte, it fully dissociates.

Recognize that the pyridinium ion (C5H5NH+) is the conjugate acid of pyridine (C5H5N). The pH of the solution is given as 2.92, which indicates the concentration of hydrogen ions (H+) in the solution.

Use the pH to find the concentration of hydrogen ions. The formula to convert pH to [H+] is: \( [H^+] = 10^{-pH} \). Substitute the given pH value into this formula to find [H+].

Since pyridinium ion is a weak acid, use the relationship between the acid dissociation constant (Ka) and the base dissociation constant (Kb) for pyridine. The formula is: \( K_a = \frac{K_w}{K_b} \), where \( K_w \) is the ion-product constant of water (1.0 × 10^-14 at 25°C). Calculate Ka using the given Kb value.

Set up the expression for the acid dissociation equilibrium: \( K_a = \frac{[H^+][C_5H_5N]}{[C_5H_5NH^+]} \). Use the calculated [H+] and the expression for Ka to solve for the initial concentration of pyridinium bromide, which is the molarity of the solution.