Hi everyone,
This is somewhat of an urgent issue and so far, my research has not produced anything concrete.
1) I am actually mixing glacial acetic acid (assumed to be pure) into distilled water, and taking measurements from there. Every single time, the pH measurement is lower than the expected value. The results are so off that it cannot be confirmed using the relationship generated by Ka = [H+][AcO-]/[AcOH]. We are getting numbers as low as 2.29 pH for a mixture of 2 mL of glacial acetic acid in 300 mL water, which implies that 60+ mL of acetic acid were added to the initial mixture. My team is out of answers. The pH probe was calibrated using standardized buffers of 3.00, 4.00, 7.00, and 10.00. We tested fresh buffers and distilled water, and had no issues reading them. The glassware is washed, dried, rinsed with distilled water. The chemicals we use are stock. One of my theories is that carbonic acid might be a culprit, but because atmospheric carbon dioxide would not enter the water in such a high quantity, the pH should be relatively unaffected. Besides that, I'm stumped.
2) I have some questions about experimental design, but I wish to resolve issue #1 first. It involves Acetic Acid - Water - Mineral Oil Equilibrium and the best ways to test it.
Both of these subjects have, if any, very little results via searching on the internet. I'm surprised to find that there is not AA-W-MO EQ data anywhere. I hope I can get some help here. Thanks.