A 30 mL sample of 0.35 mol/L bleach solution, NaOCl, is reacted with an excess of KI solution according to the following reaction equation:
2H+ + OCl- + 2I- --> Cl- + H2O + I2
The I2 produced is subsequently reacted according to the equation
2 S2O32- + I2 --> S4O62- + 2I-
What volume of 0.85 mol/L Na2S2O3 is required to titrate the I2?