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

I had a chemistry lab where we had to titrate three solutions with 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 '14 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 – Sahar Rabinoviz Jul 6 '14 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 '14 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. – Sahar Rabinoviz Jul 6 '14 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 '14 at 18:16

## 1 Answer

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? Usually deionized water is slightly acidic. I kind of mentioned that water doesn't have an equivalence point. Is there a graph without one?

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.