1. The problem statement, all variables and given/known data If you began with 8.5 mL of 0.35 M NaHCO3, how many mL of 0.10 M HCl would you need to add to get a pH 7 buffer? 2. Relevant equations pH = pKa + log([base]/[acid]) or pH = pKa + log(mmol base/mmol acid) 3. The attempt at a solution I have tried making a reaction table, but I get stuck at the beginning since I don't know how much HCl ( or H+ since the Cl^- doesn't react with water) I am starting with. By the way, the equation I have written is: HCO3^- + H^+ ---> H2CO3 (don't know if this is correct). I have also tried using the Henderson-Hasselbalch equation for buffers but that didn't give me the correct answer. Are both these methods the incorrect approach or did I maybe make a calculation error. I know I haven't shown any work, so I am just looking for some direction on how to start. Any help is much appreciated.