Question

A solution of sodium thiosulfate, Na2S2O3, is 0.4206 M. 28.94 mL of this solution reacts with 5.89 mL of I2 solution. What is the molarity of the I2 solution?

Answer 1

2S2O3^2- + I2 ==> S4O6^2- + 2I^-

mols S2O3^2- = M x L = ?
mols I2 = 1/2 that (look at the coefficients in the balanced equation)
M I2 = mols I2/L I2.