Buffer Systems
PROCEDURE
System #1 – Deionized water – NO buffer.
1. Place 10.0 mL of deionized water into each of two sample cups.
2. Measure the pH. (Should be the same in both cups – if not, they were likely not properly cleaned.)
3. Into one cup, add one drop (assume 1 drop ~ 0.05 mL) of 0.10 M HCl. Measure the pH.
4. Add an additional 9 drops of the HCl. Measure the pH.
5. Into one cup, add one drop of 0.10 M NaOH. Measure the pH.
6. Add an additional 9 drops of the NaOH. Measure the pH.
Solution Calculated pH Observed pH
DI water
DI water + 1 drop 0.1 M HCl
DI water + 10 drops 0.1 M HCl
DI water + 1 drop 0.1 M NaOH
DI water + 10 drops 0.1 M NaOH
System #2 – pH of Acetate Buffer solutions
7. Obtain ~ 40.0 mL each of acetic acid (CH3CO2H = HOAc) and sodium acetate (NaCH3CO2 = NaOAc) and put
into separate burettes.
8. Deliver 10.0 mL of each solution to separate sample cups. Measure the pH of both solutions
9. Prepare Buffer A by mixing these two solutions. Measure the pH of the buffer solution. Save this solution.
10. Prepare Buffers B and C as indicated in the table below. Measure their pH’s. Save the solutions.
pH of acetic acid: pH of acetate:
Buffer Volume (mL)
0.10 M HOAc
Volume (mL) 0.10
M NaOAc
NaOAc/HOAc log(NaOAc/HOAc) Calculated pH Observed
pH
A 10.0 10.0
B 5.0 15.0
C 15.0 5.0
