5.2: Investigating Buffers - Pre-lab

PRE-LAB QUESTIONS

1. Use the Henderson-Hasselbalch equation to perform the following calculations (K_a for acetic acid = 1.8 × 10⁻⁵, pK_a = 4.74). Show all work clearly:
   1. Buffer A Preparation: Calculate the mass of solid sodium acetate (NaC₂H₃O₂, molar mass = 82.03 g/mol) required to prepare a pH 4.00 buffer when dissolved in 50.0 mL of 0.10 M acetic acid solution.

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   2. Buffer B Preparation: Calculate the mass of solid sodium acetate (NaC₂H₃O₂) required to prepare a pH 4.00 buffer when dissolved in 50.0 mL of 1.0 M acetic acid solution.

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2. A chemist needs to prepare a buffer solution with a target pH of 6.10. Using a table of weak acid ionization constants, select the best weak acid/conjugate base pair for this buffer and justify your choice.

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3. Capacity Prediction: Buffer B contains 1.0 M acetic acid, while Buffer A contains 0.10 M acetic acid.
   • Because Buffer B is 10 times more concentrated, how many times more NaOH or HCl should Buffer B be capable of neutralizing before experiencing a 2-unit pH shift compared to Buffer A?
   • Explain why both Buffer A and Buffer B exhibit the exact same initial pH despite their 10-fold concentration difference.

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