Question

In a titration, 14.1 mL of 0.0500 M Na2S2O3 was required to turn 15.0 mL of an aqueous solution containing I2, I3-, and starch from dark blue to colorless.

How many moles of I2 and I3- were present in the solution altogether?

Answer 1

The correct formula to use for this problem is
VACA= VBCB, where VA= volume of the acid, CA= concentration of acid, VB =volume of base and CB = concentration of base.
15*CA = 14.1*0.05 =
CA = 14.1*0.05/15 = 0.047
Therefore, the number of moles (concentration) present in the solution is approximately 0.05M.