The yellow/brown coloration is due to the fomation of the triiodide (I3) ion. H2O2(aq) + 3 I(aq) + 2 H+(aq) I3(aq) + 2 H2O(l) H2O2 first oxidizes I into I2, which then combines with excess I to form the I3 complex: (1) H2O2(aq) + 2 I(aq) + 2 H+(aq) I2(aq) + 2 H2O(l) (2) I2(aq) + I(aq) I3(aq) Solution The yellow/brown coloration is due to the fomation of the triiodide (I3) ion. H2O2(aq) + 3 I(aq) + 2 H+(aq) I3(aq) + 2 H2O(l) H2O2 first oxidizes I into I2, which then combines with excess I to form the I3 complex: (1) H2O2(aq) + 2 I(aq) + 2 H+(aq) I2(aq) + 2 H2O(l) (2) I2(aq) + I(aq) I3(aq).