Question

What mass of sodium benzoate should be added to 160.0mL of a 0.17M benzoic acid solution in order to obtain a buffer with a pH of 4.30?

Answer 1

mmols benzoic acid = mL x M = 160.0 x 0.17 = approx 27 but you need to do it more accurately.
pH = pKa + log (base)/(acid)
You will need to look up the pKa for benzoic acid.
Substitute pKa, (base) = x, (acid) = 27, pH = 4.30, and solve for x = benzoate
x = mmols benzoate.
Convert to grams sodium benzoate.

Answer 2

I tried working out the problem and was unable to get the correct answer. Could you possibly work it out entirely? I don't know what I'm doing wrong.