Calculate the initial concentration of iodide ion after the solutions in tubes A and B are mixed (before the reaction begins).
Tube A
2.00 mL of 0.220 M KI
1.00 mL of 0.0100 M Na2S2O3 (starch)
1.00 mL of 0.220 M KNO3
Tube B
1.00 mL of 0.180 M K2S2O8
2.00 mL of 0.180 M K2SO4