4.5: Activity 2- Preparation of an Acetate Buffer
- Page ID
- 138919
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Per Class:
- 1 bottle stock solution of 0.1 M acetic acid (CH3COOH)
- 1 bottle stock solution of 0.1 M sodium acetate (Na+CH3COO-)
Per Group of 4:
- 6 clean 30 mL plastic tubes
- 2 clean 5 mL serological pipettes
- 2 pipette pumps (10 mL capacity)
- 1 Sharpie Marker
Procedure
- Using a sharpie marker, label the two 30 mL tubes - one as “Acetic Acid” and the other “Sodium Acetate”. Fill each tube up with the correct stock solution.
- Using a sharpie marker, label each of the two 5 ml pipettes - one as “AA” and the other as “SA”. To avoid contamination, DO NOT dip pipettes into stock solution bottles and ONLY use the designated pipette to transfer either acetic acid or sodium acetate from your group’s labeled tubes.
- Using a sharpie marker, label a clean 30 mL tube as “Buffer 1”, another as “Buffer 2”, the third as “Buffer 3”, and the fourth as “H2O”. Each student in your group will take one tube. If there are only 3 students, one of you can also take the “H2O” tube. Write your names into the first column of table 2 next to the tube(s) you will be working with.
- Create the acetate buffers using your marked serological pipettes and the specified volumes of acetic acid and sodium acetate in Table 2. Be sure to accurately pipet the volumes indicated to get good results! Review proper pipetting technique with your instructor if necessary.
(For the “\(\ce{H2O}\)” tube, simply fill the tube about a third full with pure deionized water)
- Close the lids and gently shake each tube for about 20 seconds or more to mix the contents.
- Measure the pH of each solution with the pH meter using proper technique and enter your measurements in table 2.