The kids titrated vinegar today to conclude the Acid-Base module. I used Flinn's Microscale Titration of Vinegar lab. It went better than anticipated. The main issue was the amount of phenolphthalein (PHTH). We used 25-50 drops of the vinegar and NaOH. One student used a toothpick to obtain a fraction of one drop of PHTH. The key is to use as little PHTH as possible.
We titrated vinegar because the concentration of acetic acid in household vinegar is five percent. Below is one sample titration with the calculations. The kids had results of 4.3-5.1 % concentrations. I had the kids do the dilutions and titrations. Is this a bit slow? Yes. However, I think they come away with a much clearer understanding.
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