Question

How would you prepare an acidic buffer of solution with a pH of between 4.5 and 5.0?

Answer 1

To prepare an acidic buffer with a pH between 4.5 and 5.0, mix a weak acid with a pKa near that range, like acetic acid, with its conjugate base, sodium acetate, using the Henderson-Hasselbalch equation. Measure the pH, adjust with 0.5 M HCl if needed, and titrate with 0.1 M NaOH while recording the pH to create a titration curve.

Step-by-step explanation:

Preparing an Acidic Buffer Solution

To prepare an acidic buffer with a pH between 4.5 and 5.0, one should select a weak acid with a pKa value close to the desired pH range and mix it with its conjugate base. An example of such a buffer system could be acetic acid and sodium acetate. Using the Henderson-Hasselbalch equation, which relates pH, pKa, and the ratio of conjugate base to acid, we can calculate the required proportions of each concentration.

For your specific needs, you can:

1. Mix acetic acid with sodium acetate in a ratio that provides the desired pH using the Henderson-Hasselbalch equation.
2. After preparing the buffer, measure its pH using a pH meter.
3. Add 0.5 M HCl dropwise to adjust the pH if necessary.
4. Titrate back with 0.1 M NaOH while measuring the pH to ensure it remains within the desired range.

To demonstrate accuracy and understanding of the buffer system, prepare a titration curve by recording pH values at regular intervals of NaOH addition. This will also show how well the buffer resists changes in pH upon the addition of acid or base.