Question

You have made 1.00 L of an aqueous buffer solution that is 100 mM in both sodium acetate and acetic acid. What is the pH?

Answer 1

pH = pKa = 4.75

Step-by-step explanation:

The pH of a buffer solution is calculated using Henderson Hassalbalch's equation.

The equation is:

`pH=pKa+log([salt])/([acid])`

Where

pKa = -log (Ka) = 4.75 [for acetic acid]

[salt] = concentration of salt or the conjugate base, in the given example it is sodium acetate

[acid] = concentration of acid , here it is acetic acid

As given that the concentration of both the salt and acid is same it means

`pH = 4.75+log(100)/(100)=4.75+log(1)=4.75+0=4.75`

Thus the pH of solution will be equal to its pKa.