Question

When you mix together hydrogen peroxide and iodide the resulting solution will turn yellow/brown. This is due to the formation of elemental iodine (I2). What is the cause of this color change?

Answer 1

The reason of the presence of the brown color of the solution is evidence of iodine in the reaction vessel.

• H₂O₂ (aq)   +    I- (aq)    =    H₂O (l)   +   OI^- (aq)
• H₂O₂ (aq)   +   OI- (aq)    =    H₂O (l)   +   O₂ (g)   +   I^- (aq)
• The generated oxygen interacts with the soap creating a foam “snake” which quickly fills the cylinder and spills onto the large serving tray.   Since this is an exothermic reaction, steam may be seen emerging from the cylinder. The possible presence of a brown color in the foam is evidence of iodine in the reaction vessel.
• thank you.