Chemistry+Conclusion

**The data we collected was different from our expectations.**
We expected that the swimming pool water would have a good buffering capacity, which meant the pH should not have changed drastically when small amount of acid or bases were added; otherwise, it would be very dangerous for the human skin. However, our results illustrated that the pH values of swimming pool water increased quite rapidly when the strong base NaOH was added. On the other hand, the pH values of swimming pool water didn't decrease as fast when the strong acid HCl was added. We couldn't find the reasons why that happened.

From the data of adding ten drops of NaOH, Sample S had the best buffering capacity since it had the least change in pH values, which was 9.52 - 6.98, or 2.12. But from the data of adding ten drops of HCl, sample B had the best buffering capacity since it had the least change in pH values, which was 7.25 - 6.85, or 0.4. If we combined both data of adding NaOH and HCl and took the average change in pH values, sample T had the best buffering capacity. pH values of sample T only changed by 1.4, whereas sample B changed by 1.52 and sample S changed by 1.56.