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
Use the Henderson-Hasselbalch equation. base is sodium acetate. acid is acetic acid.
To find the pH of a buffer solution, you need to use the Henderson-Hasselbalch equation:
pH = pKa + log ([A-]/[HA])
In this case, Acetic acid (CH3COOH) is the weak acid, and Sodium acetate (CH3COONa) is its conjugate base.
Given:
- Concentration of Acetic acid (HA) = 0.125 M
- Concentration of Sodium acetate (A-) = 0.250 M
- pKa of Acetic acid = 4.76
Step 1: Calculate [A-]/[HA]
[A-]/[HA] = (concentration of A-)/(concentration of HA)
[A-]/[HA] = (0.250 M)/(0.125 M)
[A-]/[HA] = 2
Step 2: Apply the Henderson-Hasselbalch equation
pH = pKa + log ([A-]/[HA])
pH = 4.76 + log(2)
Step 3: Calculate the log value
log(2) = 0.301
Step 4: Substitute the value in the equation
pH = 4.76 + 0.301
pH = 5.061
Therefore, the pH of the buffer solution is approximately 5.061.
ph = PK + log (base concentration/acid concentration)
pH =4.76 + log (.250/.125)
pH = 4.76 = Log (2)