You are asked to prepare a buffer solution with a pH of...

You are asked to prepare a buffer solution with a pH of 3.50. The following solutions, all $0.100 \mathrm{M}$, are available to you: HCOOH, $\mathrm{CH}_{3} \mathrm{COOH}, \mathrm{H}_{3} \mathrm{PO}_{4}, \mathrm{NaHCOO}$ $\mathrm{NaCH}_{3} \mathrm{COO},$ and $\mathrm{NaH}_{2} \mathrm{PO}_{4} . \quad$ Describe how you would prepare this buffer solution. [Hint: What volumes of which solutions would you use?]

You are asked to prepare a buffer solution with a pH of 3.50. The following solutions, all $0.100 \mathrm{M}$, are available to you: HCOOH, $\mathrm{CH}_{3} \mathrm{COOH}, \mathrm{H}_{3} \mathrm{PO}_{4}, \mathrm{NaHCOO}$
$\mathrm{NaCH}_{3} \mathrm{COO},$ and $\mathrm{NaH}_{2} \mathrm{PO}_{4} . \quad$ Describe how you
would prepare this buffer solution. [Hint: What volumes of which solutions would you use?]

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Key Concepts

Buffer Solution

A buffer solution is made by mixing a weak acid with its conjugate base (or a weak base with its conjugate acid) to resist drastic changes in pH when small amounts of strong acid or base are added. Buffers are critical in many chemical and biological systems to maintain a stable pH environment.

Henderson-Hasselbalch Equation

The Henderson-Hasselbalch equation, expressed as pH = pKa + log([A–]/[HA]), is used to relate the pH of a buffer solution to the concentrations of the weak acid (HA) and its conjugate base (A–). This equation assists in calculating the required ratio of acid to base to achieve a desired pH.

Weak Acid and Conjugate Base Pair Selection

When preparing a buffer, it is essential to choose a weak acid and its conjugate base whose pKa is close to the target pH. This ensures that the buffer has effective capacity in the desired pH range and can maintain stability against pH changes.

Stock Solution Dilution and Mixing

Preparing a buffer from concentrated stock solutions involves calculating the necessary volumes to mix, based on both the desired molarity and the acid to base ratio determined from the Henderson-Hasselbalch equation. This process ensures that the final buffer solution has the correct concentration and pH.

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