The active ingredient in aspirin is acetylsalicylic acid. A 2.00 g sample of acetylsalicylic acid required 21.76 mL of 0.5101 M NaOH for complete reaction. Addition of 12.43 mL of 0.4466 M HCl to the flask containing the aspirin and the sodium hydroxide produced a mixture with pH = 3.48. Find its Ka value. Acetylsalicylic acid is a monoprotic acid.