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 Weak Bases

General Chemistry

17. Acid and Base Equilibrium

pH of Weak Bases

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Multiple Choice

15.3 grams of sodium benzoate is dissolved in 250 mL of water. What is the pH of the resultant solution if the Kb of benzoate ion is 1.5 x 10^-10?

9.20

6.50

7.00

8.10

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Verified step by step guidance

Calculate the molar mass of sodium benzoate (C7H5NaO2) by adding the atomic masses of its constituent elements: C (12.01 g/mol), H (1.01 g/mol), Na (22.99 g/mol), and O (16.00 g/mol).

Determine the number of moles of sodium benzoate by dividing the given mass (15.3 grams) by its molar mass.

Calculate the concentration of sodium benzoate in the solution by dividing the number of moles by the volume of the solution in liters (0.250 L).

Write the equilibrium expression for the hydrolysis of the benzoate ion (C6H5COO-) in water, which forms benzoic acid (C6H5COOH) and hydroxide ions (OH-). Use the given Kb value to set up the expression: Kb = [C6H5COOH][OH-] / [C6H5COO-].

Assume that the change in concentration of benzoate ion is small compared to its initial concentration, and solve for [OH-] using the Kb expression. Then, calculate the pOH of the solution and use the relation pH + pOH = 14 to find the pH.