Simple pH Problem (If I could remember)

[negatifzeo]

Homework Statement

If one mixed 100mL of .1M Sodium acetate with 100 mL of .1M acetic acid, the pH of the solution would be 4.7 If 60 mL of .1M NaOH were added to this solution, what would be it's pH?

Homework Equations

Henderson Hasselback
pH=pKa+ log(base/acid)

The Attempt at a Solution

I haven't really made one because I'm not sure how to proceed. The thing that really confuses me is the pKa part of henderson-hasselbach. When we are dealing with solutions having more more than one pkA, which pkA do we use? I know I did a ton of these problems in Gen Chem but can't remember how!

 

[Bohrok]

There's only one thing (ignoring water) that has a pKa: the acetic acid. Since acetic acid is monoprotic, it has only one pKa.