Answer:
6.6 is the [tex]pK_a[/tex] of the weak acid.
Explanation:
To calculate the pH of acidic buffer, we use the equation given by Henderson Hasselbalch:
[tex]pH=pK_a+\log(\frac{[salt]}{[acid]})[/tex]
We are given:
[tex]pK_a[/tex] = negative logarithm of acid dissociation constant =?
The ratio of conjugate base to acid is = [tex]\frac{[salt]}{acid}=4[/tex]
pH = 7.2
Putting values in above equation, we get:
[tex]7.2=pK_a+\log(4)[/tex]
[tex]pK_a=7.2-\log(4)=6.598\approx 6.6[/tex]
6.6 is the [tex]pK_a[/tex] of the weak acid.
