In Lab 9, students performed acid-base titrations. Redox reactions can also be used in titrations. An example is the titration of ascorbic acid (H2C6H6O6) in lemon juice using triiodide (I3-). A starch indicator will turn the solution blue-black at the endpoint. The half-reactions involved are shown below.
C6H6O6 + 2 H+ + 2 e- ? H2C6H6O6 +0.06 V
I3- + 2 e- ? 3 I- +0.53 V
Use the data given below to determine the amount of ascorbic acid in lemon juice. (Note: The recommended daily allowance of ascorbic acid (Vitamin C) is 90 mg.)
Data Table P6: Titration of ascorbic acid in lemon juice with triiodide
concentration of I3- 0.0190 M
volume lemon juice 93.05 mL
mass lemon juice 94.72 g
equivalence volume of I3- 16.26 mL
mmol of I3- _____________?_________mmol
mmol of H2C6H6O6 _______?_________mmol
mass of H2C6H6O6 ________?________mg