Question

I need to calculate the buffer capacity in acid and in a base from these data. Then I need to write a short paragraph ( 7 sentences) explaining what happen and why one is better buffer that the other.

Buffer Capacity = (number of moles of OH- or H3O+ added)

                   (pH change)(volume of buffer in L)

Buffer capacity in acid 25.0 ml of 0.10M acetic acid and 0.10 M Sodium acetate solution

Buffer Volume	25.0mL
Buffer pH	4.5
Buffer capacity

Vol HCl 0.1M added	Ph
17mL	4.5
21.4	4.5
23.6	4.5
26.5	4.0
28.4	4.0
30.4	3.5
32.3	3.5

Buffer capacity in base

Buffer Volume	25.0mL
Buffer pH	4.5
Buffer capacity

Vol NaOH 0.1M added	Ph
34.9	4.5
36.8	4.5
38.6	5.0
39.9	5.0
41.5	5.0
42.8	5.5
44.1 mL Final volume	5.5

Type your answer plase

Answer 1

Buffer capacity = number of moles of acid or base added per liter solution / change in pH of the buffer
or
Buffer capacity = number of milli equivalents of acid or base added / change in pH
For Acid addition,
since pH change = 0 for addition of 17mL, 21.4 mL and 23.6 mL of 0.1 M HCl solution.
so buffer capacity = constsnt / 0 = infinity
buffer capacity = 26.5 * 0.1 / 0.5 = 5.3
buffer capacity = 28.4 * 0.1 / 0.5 = 5.68
buffer capacity = 30.4 * 0.1 / 1 = 3.04
buffer capacity = 32.3 * 0.1 / 1 = 3.23
For Base addition,
since pH change = 0 for addition of 34.9mL and 36.8 mL of 0.1 M NaOH solution.
so buffer capacity = constsnt / 0 = infinity
buffer capacity = 38.6 * 0.1 / 0.5 = 7.72
buffer capacity = 39.9 * 0.1 / 0.5 = 7.98
buffer capacity = 41.5 * 0.1 / 0.5 = 8.3
buffer capacity = 42.8 * 0.1 / 1 = 4.28
buffer capacity = 44.1 * 0.1 / 1 = 4.41
According definition of buffer capacity = 1 then that buffer acts as better buffer solution. In the given acid and base addition the buffer capacity is minimum when acid addition buffer capacity = 3.04 so Acid buffer is best buffer in the given two buffer solutions