Question

The acetic acid and sodium acetate solutions will have concentrations of 0.50 M.

1. Calculate Concentrations of acetic acid and sodium acetate in the prepared buffer solutions in Part I as noted in the following table:

Solution	Voluem of Acetic Acid (mL)	Volume of Sodium Acetate (mL)
A	25	25
B	45	5
C	5	45
W	0	0

2. Calculate Theoretical pH of prepared buffer solutions

Answer 1

BUffer A

V acid = 25 mL and molarity 0f acid = 0.50M

V acetate = 25 mL and molarity = 0.5

Thus [acid ] in the buffer = 25x0.5/50

= 0.25 M

and [acetate ] in the buffer = 25x0.5 /50

= 0.25M

The pH of buffer is calculated by Hendersen equation

pH = pKa + log [conjugate base]/[acid]

= 4.74 + log 0.25/0.25

= 4.74

Buffer B

[acid] = 45x0.5/50 =

= 0.45 M

[acetate] = 5 x0.5 /50

= 0.05

Thus pH = 4.74 + log 0.05/0.45

= 3.785

Buffer C

[acid] = 5x0.5/50

= 0.05 M

[acetate] = 45x0.5/50

= 0.45

Thus pH = 4.74 + log 0.45/0.05

=5.694