Buffer Solutions Investigation

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Buffer solution beakers and pH meter illustration

📚 Part 1: Buffer Theory and Concepts

1. What is a buffer solution?

A solution that maintains a constant pH when diluted

A solution that resists changes in pH when small amounts of acid or alkali are added

A solution containing only strong acids and bases

A solution with a pH of exactly 7

2. Which combination would form an effective acidic buffer?

HCl and NaCl

CH₃COOH and CH₃COONa

NaOH and NaCl

H₂SO₄ and Na₂SO₄

3. Complete the equilibrium equation for an ethanoic acid buffer system:

CH₃COOH(aq) ⇌ _____________ + _____________

4. Explain how a buffer solution resists pH changes when a small amount of acid is added:

🧮 Part 2: Henderson-Hasselbalch Calculations

5. The Henderson-Hasselbalch equation is: pH = pKₐ + log([A⁻]/[HA])

Calculate the pH of a buffer containing 0.10 M CH₃COOH and 0.15 M CH₃COONa.

(Given: pKₐ for ethanoic acid = 4.76)

6. A buffer solution has a pH of 5.2 and contains 0.20 M ethanoic acid.

Calculate the concentration of ethanoate ions required. (pKₐ = 4.76)

7. Calculate the pH of a phosphate buffer system containing 0.050 M H₂PO₄⁻ and 0.025 M HPO₄²⁻.

(Given: pKₐ₂ for phosphoric acid = 7.21)

8. A formic acid buffer (HCOOH/HCOO⁻) has a pH of 3.5.

If [HCOOH] = 0.30 M, calculate [HCOO⁻]. (Given: pKₐ for formic acid = 3.75)

9. Calculate the ratio [A⁻]/[HA] required to prepare a buffer with pH = 4.0 using ethanoic acid.

(Given: pKₐ = 4.76)

10. A buffer contains 0.080 M NH₃ and 0.120 M NH₄Cl.

Calculate the pH of this basic buffer. (Given: pKᵦ for NH₃ = 4.75, pKw = 14.00)

🔬 Part 3: Advanced Buffer Calculations

11. A buffer is prepared by mixing 250 mL of 0.20 M CH₃COOH with 150 mL of 0.15 M NaOH.

Calculate the pH of the resulting buffer solution. (pKₐ = 4.76)

12. Calculate the change in pH when 10.0 mL of 0.10 M HCl is added to 100 mL of a buffer containing 0.25 M CH₃COOH and 0.20 M CH₃COONa.

(Given: pKₐ = 4.76)

13. What mass of sodium ethanoate (CH₃COONa) must be added to 500 mL of 0.15 M ethanoic acid to create a buffer with pH = 5.0?

(Given: pKₐ = 4.76, Mr of CH₃COONa = 82.0 g/mol)

🔬 Part 4: Practical Investigation and Applications

14. In your practical investigation, you added 2 cm³ of 0.1 M HCl to both pure water and a buffer solution. Predict the results:

Pure water pH change: from 7.0 to approximately _______

Buffer solution pH change: from 4.8 to approximately _______

15. Which of these are important biological buffer systems? (Tick all that apply)

Bicarbonate buffer in blood

Phosphate buffer in cells

Protein buffers

Sodium chloride in tears

16. Explain why buffer systems are essential in biological processes:

17. Describe one limitation of buffer solutions and suggest how this might be overcome in industrial applications:

Buffer Solutions Investigation

Buffer Solutions Investigation

📚 Part 1: Buffer Theory and Concepts

🧮 Part 2: Henderson-Hasselbalch Calculations

🔬 Part 3: Advanced Buffer Calculations

🔬 Part 4: Practical Investigation and Applications

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