[SinkingTako]

When Fe²⁺ is reacted with H₂O₂, in the presence of H+, the following reaction should take place:

2Fe²⁺ +H₂O₂ +2H⁺  2Fe³+ +2H₂O

However, in the lab, When H₂O₂ is added to the apple green solution of Fe²⁺ (without any acid), the solution turns orange, which is very very similar in colour to that of the Fe³⁺ solution. When acid is added, the solution changes colour back to the apple green.

Yet I think the green solution of H₂O₂, acid and Fe²⁺ formed is not simply Fe²⁺ again. When NaOH is added, a almost black ppt is formed, which is distinctly different from the brick-red ppt of Fe(OH)₃, or dirty green ppt of Fe(OH)₂. Also HCl (which is the acid I used) would definitely not been able to reduce Fe³⁺ to Fe ²⁺ again.

What can this black solid be, and what is the reaction of H₂O₂ and Fe²⁺?

[Hunter2]

Fenton reaction

http://en.wikipedia.org/wiki/Fenton%27s_reagent