[aannrr]

So for my chemistry lab we had to create a 100 ml of two buffers with the same pH but significantly different capacities. My partner and I decided to use acetic acid and sodium acetate to create our buffer. We used 50 ml of 1.0 M acetic acid and 4.1 g of sodium acetate dissolved in 50 ml of distilled water. We added these together into a large beaker(A) to create a 100 ml buffer solution. We then took 25 ml out of the large beaker and put it into another large beaker(B). We then diluted the other beaker(B) with 75 ml of distilled water. We then diluted the original beaker(A) with 25 ml of distilled water. So all in all we have two large beakers both with a buffer of acetic acid and sodium acetate just at different concentrations (One has 75 ml of the buffer solution while one has 25 ml of the buffer solution both diluted to 100 ml). We then added 20 ml of 1.0 M sodium hydroxide to each beaker. We repeated all the steps above except we used 1.0 M hydrochloric acid instead of sodium hydroxide. The problem that I am having is calculating the theoretical pH that I should be getting when performing this lab. We are using the Henderson–Hasselbalch equation.

[Borek]

http://www.chembuddy.com/?left=buffers&right=pH-change

But if you have exceeded buffer capacity, the final pH will be almost solely just a function of the excess acid/base added.

Please note, the ionic strengths are so high you will be several tenths of a unit off.