Question

Did your buffer have a larger capacity for acid or base? Why?

Buffer Capacity pH 6.66 6.54 6.41 6.28 Moles -4.76E-03 -9.09E-03 -1.30E-02 -1.67E-02 -2.00E-02 -2.31E-02 -2.59E-02 -2.86E-02 4.76E-03 9.09E-03 1.30E-02 1.67E-02 2.00E-02 2.31E-02 2.59E-02 2.86E-02 3.10E-02 6.11 5.89 5.56 4.62 6.87 6.96 7.05 7.16 7.27 7.44 7.66 8.04 9.02 -4.00E-02 -3.00E-02 -2.00E-02 2.00E-02 3.00E-02 4.00E-02 -1.00E-02 0.00E+00 1.00E-02 Moles Acid/Moles Base

Answer 1

Prepare the following table.

Moles acid/base added	Δ(moles acid/base added)	pH	ΔpH
0.00476	-	6.66	-
0.00909	0.00433	6.54	-0.12
0.01300	0.00391	6.41	-0.13
0.01670	0.00370	6.28	-0.13
0.02000	0.00330	6.11	-0.13
0.02310	0.00310	5.89	-0.22
0.02590	0.00280	5.56	-0.33
0.02860	0.00270	4.62	-0.94
0.00476	-	6.87	-
0.00909	0.00433	6.96	0.09
0.01300	0.00391	7.05	0.09
0.01670	0.00370	7.16	0.11
0.02000	0.00330	7.27	0.11
0.02310	0.00310	7.44	0.17
0.02590	0.00280	7.66	0.22
0.02860	0.00270	8.04	0.38
0.03100	0.00240	9.02	0.98

The buffer capacity of a buffer is defined as the ability of the buffer to resist changes in pH of the buffer due to addition of small amounts of a strong acid or base. The buffer depicted here shows very small variations in pH when small amounts of the strong base are added (the first six readings in the last column). Hence, the buffer has a better capacity to neutralize a strong base or the buffer has a better capacity for the strong base.