In a lab experiment, we experimented with 1% glucose solution and Sorenson's solution to determine pH levels and whatnot; the other part of the lab was to determine which one, if either, was a buffering solution. According to the notes my instructor gave us, a buffers are mixtures of chemicals (a weak acid and its conjugate base) that prevent a change in the number of available hydrogen ions or hydroxyl ions in solution (in other words, it helps maintain the pH of the solution.)

Question

So we first measured the pH of the 1% glucose solution after every 10 mL of HCl added until there were 50 mL of HCl added total. We then did the same thing, but instead of glucose we used Sorenson's solution, and added HCl to that until 50 mL total were added. The thing that confused me though was that the pH level of each solution rose at somewhat the same increments as each other. Should this have happened? Because I don't see how one could determine which one was a buffering solution just based off of these numbers because they both rose at almost the same rate.

Answer 1

Your going to have to take a look at a titration curve to understand what you did. But providing your data may allow someone to give you a better answer.

Answer 2

I had to think about your question for a bit. Usually, you add a strong base to see an increase in the pH for a titration, but in this experiment you added a strong acid and saw an increase in the pH; this should not have been the case. It seems as though you were adding a strong acid to a basic buffer solution and you should have seen small decreases in the pH, because the buffer shifts the equilibrium to resist the change in pH. I believe what you were measuring is the pOH, which should have increased with the addition of the strong acid, but only incrementally. I am not sure because you did not provide data, but your experiment was to see which solution was a better basic buffer. If that is the case, then the one that resisted the change in the pOH.