What is the pH of a buffer solution of 0.125M Acetic acid and 0.250M Sodium acetate? the Pk of Acetic acid is 4.76
To find the pH of a buffer solution, we can use the Henderson-Hasselbalch equation:
pH = pKa + log ([A-] / [HA])
Where:
pH is the pH of the solution
pKa is the logarithmic value of the acid dissociation constant (Ka) of the acid
[A-] is the concentration of the conjugate base
[HA] is the concentration of the acid
In this case, acetic acid (CH3COOH) is the acid, and sodium acetate (CH3COONa) is its conjugate base (CH3COO-).
Given:
[HA] = 0.125 M (concentration of acetic acid)
[A-] = 0.250 M (concentration of sodium acetate)
pKa = 4.76 (acid dissociation constant of acetic acid)
Using the Henderson-Hasselbalch equation:
pH = 4.76 + log (0.250 / 0.125)
Calculating the value inside the logarithm:
(0.250 / 0.125) = 2
Simplifying the equation:
pH = 4.76 + log (2)
Using logarithmic properties, log (2) is approximately 0.3010:
pH = 4.76 + 0.3010
Calculating:
pH ≈ 5.06
Therefore, the pH of the buffer solution is approximately 5.06.