Chemistry
posted by D.J. .
What is the pH of a buffer solution that is made by adding 21.0 grams of sodium fluoride to 1.00 Liter of 0.15M hydrofluoric acid? (see the Table above for the Ka of hydrofluoric acid; calculate the pH to 2 decimal places) hint: you will have to find the molarity of NaF in this solution.
Acid Dissociation Constant:
HF 6.6 x 104

Use the HendersonHasselbalch equation.

How? Im seeing the equation but what and where do i plug in?

pH = pKa + log (base)/(acid)
pH = ?
pKa you have (or can calculate it from Ka).
base = NaF and molarity NaF = mols/L. You have grams, convert to mols.
acid you have in M now.
Plug and chug. 
thanks