# Differentiating between Titration, Buffer, diluted buffer, Deionized H₂O

I had a chemistry lab where we had to titrate three solutions with $$\ce{HCl}$$: a buffer, a diluted buffer and deionized water. My partner and I didn't label the charts we made, so now I have to figure out which one is which.

The way I see is that from the Henderson-Hasselbalch equation: $$\mathrm{p}\ce{H} = \mathrm{p}K_a + \log\left(\ce{[A^{-}]/[HA]}\right)$$, the diluted buffer should have a larger slope at the beginning then the original buffer solution.

My question is, is my logic correct, and how do I differentiate between the original buffer and the deionized water?

• What is the expected pH of deionized water and what would the pH be after adding a few drops of acid? For both buffer solutions, there is an equivalence point, how would you use that to tell them apart?
– LDC3
Jul 6, 2014 at 17:56
• pH of water is expected to be close to be near 7 however two my initial pH's were around 4.6 and the other was around 4.2. I would expect the equivalence point to occur sooner for the diluted buffer Jul 6, 2014 at 18:04
• Usually deionized water is slightly acidic. I kind of mentioned that water doesn't have an equivalence point. Is there a graph without one?
– LDC3
Jul 6, 2014 at 18:09
• One obviously has an equivalence point, while the other two appear to drop rapidly after adding one drop of HCl, although one drops much more quickly then the other. Jul 6, 2014 at 18:12
• I guess your diluted buffer is more diluted than I thought. What is the purpose of a buffer? A diluted buffer would have the same characteristic, but in a smaller amount. Water would be missing this characteristic. You should be able to figure out which graph is which now.
– LDC3
Jul 6, 2014 at 18:16