Question

I understand part (I) but We have only briefly gone over the HH equation in class and I understand how to use it to get the pH but I really don't understand how to use it in part (II), assuming I should be using it in this question?

(I)Calculate the pH of an acetate buffer containing 27.5 mM acetic acid (pKa is 4.74) and 50 mM
sodium acetate.

(II) When a 100 mM aq solution of sodium acetate was prepared in the lab it had a
pH of 8.9. Calculate the amount of acetic acid (in g) to be added to 0.5 L of this sodium acetate
solution in order to bring its pH to the target value of 5.00.

Answer 1

For part II, plug into the HH equation.
5.00 = 4.74 + log (base)/(acid)
5.00 = 4.74 + log (100*0.5)/(x)
Solve for x = mmols acetic acid and convert that to grams acetic acid.