If I start out with 100 mM acetic acid, what substance (to a final concentration of 1 M) could I add to change the pH considerably? I was thinking of NaCl or ethanol or acetone. Substances added should not be acids or bases, i.e. a 1 M solution of them should have a pH close to neutral. I'm asking because I am trying to create a demonstration on how pH calculations are just approximations under non-ideal conditions.
The acetic acid should not undergo an chemical reaction (other than acid/base). I would use a pH meter to monitor the pH. I would have a control where I increase the volume to match the experiment where I add a substance that influences the pH (or dissolve the substance in 100 mM acetic acid to keep the acetic acid concentration constant).
I am looking for changes in pH based on non-ideal behavior. The concentration of acetic acid should remain the same, and there should not be any neutralization reaction. In other words, the calculate pH should stay at 2.87 (assuming ideal conditions) while the measured pH would change.