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

18. Aqueous Equilibrium

Henderson-Hasselbalch Equation

General Chemistry

18. Aqueous Equilibrium

Henderson-Hasselbalch Equation

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Multiple Choice

Consider a buffer solution that is 0.50 M in NH3 and 0.20 M in NH4Cl. For ammonia, pKb = 4.75. Calculate the pH of 1.0 L of the solution upon addition of 0.010 mol of solid NaOH to the original buffer solution.

8.75

9.00

9.26

8.50

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Verified step by step guidance

Identify the components of the buffer solution: NH3 (ammonia) and NH4Cl (ammonium chloride). NH3 is a weak base, and NH4+ is its conjugate acid.

Use the Henderson-Hasselbalch equation for a buffer solution: \( \text{pH} = \text{pKa} + \log \left( \frac{[\text{base}]}{[\text{acid}]} \right) \). First, calculate \( \text{pKa} \) from \( \text{pKb} \) using the relation \( \text{pKa} + \text{pKb} = 14 \). Therefore, \( \text{pKa} = 14 - 4.75 = 9.25 \).

Determine the initial concentrations of NH3 and NH4+ in the buffer solution. NH3 is 0.50 M and NH4+ is 0.20 M.

Calculate the change in concentration of NH3 and NH4+ upon addition of NaOH. NaOH will react with NH4+ to form NH3 and water: \( \text{NH4}^+ + \text{OH}^- \rightarrow \text{NH3} + \text{H2O} \). The amount of NaOH added is 0.010 mol, which will decrease the concentration of NH4+ by 0.010 M and increase the concentration of NH3 by 0.010 M.

Substitute the new concentrations into the Henderson-Hasselbalch equation: \( \text{pH} = 9.25 + \log \left( \frac{0.50 + 0.010}{0.20 - 0.010} \right) \). Calculate the logarithmic term to find the pH of the solution after the addition of NaOH.