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 30.0 mL of 1.0 M HCl to the original buffer solution.

pH = 9.25

pH = 8.75

pH = 8.95

pH = 9.05

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Verified step by step guidance

Identify the components of the buffer solution: NH3 (ammonia) is the weak base, and NH4Cl provides the conjugate acid NH4+. The initial concentrations are 0.50 M for NH3 and 0.20 M for NH4+.

Calculate the moles of NH3 and NH4+ in the buffer solution. Since the volume of the solution is 1.0 L, the moles of NH3 are 0.50 mol and the moles of NH4+ are 0.20 mol.

Determine the moles of HCl added to the solution. With a concentration of 1.0 M and a volume of 30.0 mL (0.030 L), the moles of HCl are 0.030 mol.

When HCl is added to the buffer, it reacts with NH3 to form NH4+. The reaction is: NH3 + HCl → NH4+ + Cl-. Calculate the new moles of NH3 and NH4+ after the reaction. Subtract 0.030 mol from the initial moles of NH3 and add 0.030 mol to the initial moles of NH4+.

Use the Henderson-Hasselbalch equation to calculate the pH of the buffer solution: \( \text{pH} = \text{pK}_\text{a} + \log \left( \frac{[\text{Base}]}{[\text{Acid}]} \right) \). First, find \( \text{pK}_\text{a} \) using \( \text{pK}_\text{a} = 14 - \text{pK}_\text{b} \). Then, substitute the concentrations of NH3 and NH4+ into the equation to find the pH.