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

Intro to Buffers

General Chemistry

18. Aqueous Equilibrium

Intro to Buffers

Previous problemNext problem

Struggling with General Chemistry?

Join thousands of students who trust us to help them ace their exams!Watch the first video

Multiple Choice

A buffer solution is prepared by adding 9.04 mL of 1.27 M HBr to 190.0 mL of 0.11 M methylamine solution. The buffer is allowed time to establish. Then, 0.005 mol of a strong base is added. What is the pH of the resulting solution? Round your answer to 2 decimal places.

8.75

9.85

7.50

10.45

Previous problemNext problem

Verified step by step guidance

Identify the components of the buffer solution: HBr is a strong acid, and methylamine (CH3NH2) is a weak base. The buffer is formed by the reaction of HBr with methylamine to form methylammonium bromide (CH3NH3Br).

Calculate the initial moles of HBr and methylamine. Use the formula: \( \text{moles} = \text{concentration} \times \text{volume} \). For HBr: \( 9.04 \text{ mL} = 0.00904 \text{ L} \), so \( \text{moles of HBr} = 1.27 \text{ M} \times 0.00904 \text{ L} \). For methylamine: \( 190.0 \text{ mL} = 0.190 \text{ L} \), so \( \text{moles of CH3NH2} = 0.11 \text{ M} \times 0.190 \text{ L} \).

Determine the moles of methylammonium ion (CH3NH3+) formed by the reaction of HBr with methylamine. Since HBr is a strong acid, it will react completely with methylamine. Subtract the moles of HBr from the moles of methylamine to find the remaining moles of CH3NH2 and the moles of CH3NH3+ formed.

Add the moles of the strong base (0.005 mol) to the buffer solution. The strong base will react with the methylammonium ion (CH3NH3+) to form additional methylamine (CH3NH2) and water. Adjust the moles of CH3NH3+ and CH3NH2 accordingly.

Use the Henderson-Hasselbalch equation to calculate the pH of the buffer solution: \( \text{pH} = \text{pK}_a + \log \left( \frac{[\text{base}]}{[\text{acid}]} \right) \). The \( \text{pK}_a \) of methylammonium ion is needed, and the concentrations of CH3NH2 and CH3NH3+ are calculated from their moles and the total volume of the solution.