How many mL of 0.1 M HCl must be added to 100 mL of 0.1 M F- to prepare a buffer solution that has a pH of 3.05? Ka= 6.8×10^-4. please write it out on paper. i know you need to use pH=pKa+log(conj. base/acid). I do not know what to plug in for conjugate base and the acid.