Hcl, A Salt Of A Strong Acid-Strong Base

1. In step 1 HCl, a strong acid, was added one drop at a time to DI water. The addition of HCl to the DI water resulted in the pH going down. The first drop of HCl that was added caused the pH to go from 5.24 down to 4.20. The second drop caused the pH to go to 3.92, followed by the third drop which caused the pH to go to 3.79. The overall addition of HCl caused a 1.45 drop in pH.

2. Step 2 was the same as step 1 but NaCl, a salt of a strong acid-strong base, was used in replace of DI water. The addition of NaCl slightly buffered the pH but not so much so that the pH did not drop at all. This is because NaCl is a neutral salt, it is composed of an alkaline metal and a halide which neither effect H+. Which explains why the pH still went down

In step 4 NaOH, a strong base, was added drop by drop to NaCl, a salt of a strong acid-strong base. The addition of NaOH to NaCl resulted in the pH dramatically going up which is the opposite of what happened in step 1. The initial pH of NaCl was 4.71 and when just one drop of NaOH was added the pH went up to 5.14. After all three drops of NaOH were added to NaCl the pH was tested to be 8.21, the highest pH so far. So the NaCl most certainty did not buffer the pH changes. Also step 4 had the largest overall magnitude of change in pH, of 3.5, over double the change in step 1.

5. Step 5 was similar to step 1 but instead of adding HCl to DI water, HCl was added to an acetic acid–acetate ion buffer. By using an acetic acid-acetate ion buffer in replace of DI water when HCl was added caused the pH to barely even change. The initial pH of the acetic acid-acetate ion buffer was 4.75 and when the first drop of HCl was added the pH went down like in step 1 but only .02. After all three drops of HCl were added, the pH was tested to be the exact same as the initial pH. This is not like what happened in step 1 where the pH went down 1.45 by the third drop of HCl.

CH3COO-(aq) + H+(aq) ↔

CH3COOH(aq) + OH-(aq) ↔ CH3COO–(aq) + H2O(l)

7. Step 7 was similar to step 1 but instead of adding HCl to DI water, in step 7 HCl was added to an ammonia-ammonium ion buffer. When HCl was added to the ammonia-ammonium ion buffer the pH remained the same which is not like step 1 where the pH went down. The pH of the ammonia-ammonium ion buffer was originally 9.30 and though it fluacted .01 drop 1 and 2, by drop 3 it was once again 9.30. This is not like what happened in step 1 where the pH consistently went down and by drop 3 of HCl the pH had gone down 1.45.

NH3(aq) + H+(aq) ↔ NH4+(aq)

8. In step 8, NaOH was added a drop at a time to an ammonia-ammonium ion buffer. By adding NaOH to the ammonia-ammonium ion buffer caused the pH to nearly stay the same, unlike what happened in step 1 where the pH went down after HCl was added. The pH of the ammonia-ammonium ion buffer was initially 9.40 and by the third drop the pH was 9.41, which is only a .01 increase in pH. This is unlike what occurred in step 1 where by the third drop of HCl the pH had increased