The following volumes were pipetted into reaction flasks and mixed: 10.0 mL 0.0100 M KI, 10.0 mL 0.00100 M Na2S2O3, 20.0 mL 0.0400 M KBrO3, and 10.0 mL 0.100 M HCl. The mixture turned blue in 66.5 seconds.
Calculate the concentrations of all reacting ions the instant after mixing the two flasks, but before any reaction takes place.