Mass of aspirin tablet (g) = 0.43 Volume of hydrochloric acid required in back titration (ml) = 2.0 Concentration of NaOH = 0.179 M Concentration of HCl6) % of acetylsalicylic acid= 0.018 g / 0.43 g = 4.19 %. What am I doing wrong? this can't be right. Update: 1) Use a 50–mL volumetric pipette...