What is the pH of the solution that results from mixing 5 ml of 0.2 M NaOH and 100 mL of 0.05 M lactic acid? (Pka of lactic acid= 3.86)

Use the Henderson-Hasselbalch equation. Th e mixture you have indicated will react to form a buffer, the base will be the sodium lactate and the acid will be the lactic acid not neutralized by the NaOH. Post your work if you get stuck.