I have three mixtures comprised of some part acid and some part base, creating b
ID: 483601 • Letter: I
Question
I have three mixtures comprised of some part acid and some part base, creating buffer solutions. To one portion of each of these solutions, drops of HCL were added one at a time, and the resultant pH recorded. This was repeated for other solutions with the same parts acid/base but NaOH was added, and pH recorded. This drop procedure was repeated with water, and an unknown, and pH recorded. Now that I have all the pH's recorded for various amounts of added high concentration acid or base, I need to determine whether or not my unknown was pure water, or one of the acid/base pairs from another table. How would I know what my unknown was?
(Possible unknowns Glycine (2.3pKa),Glycine(9.6pKa2) Acetice Acid (4.75pKa), Phosphate buffer(2.15pKa),Phosphate buffer(6.82pKa2),Phosphate buffer(12.38pKa3)
Table 2: pH when strong acid or base is added dropwise to varous solutions drops HCL Mixture i Mixture 2 Mixture 3 water unknown o 5.94 6.72 785 7.48 5.88 1 5.8 6.66 2.76 7.72 2.82 2 5.45 6.6 7.61 2.58 2.54. 3 4.54 6.54 7.52 2.46 2.4 4 2.37 2.31 3.55 7.43 6.47 5 3.24. 6.39 7.35 2.3 2.25 drops NaoH Mixture 1 Mixture 2 Mixture 3 Water Unknown 0 5.94 6.72 7.85 5.88 7.48 1 7.93 10.48 10.53 6.01 6.74. 2 6.1 6.78 8.24 10.84 10.86 3 8.88 11.06 11.05 6.17 6.85 6.9 10.17 22 11.22 6.25 6.96 10.55 11.33 11.31 6.73Explanation / Answer
When a small amount of acid or base is added to a buffer, no significant ph change occurs. If you see your pH table for unknown,when you added 1 drop HCl or NaOH, there is a significant amount of pH change. where as if you se mixture 1,2 and 3 , no significant amount of pH change has occured ener after adding 5 drops of Hcl or NaOH.
So, the unknown u are using is pure water.