Edexcel IAL Chemistry A2 17.31 Fe2+ catalysis of iodide and peroxodisulfate
Edexcel IAL Chemistry A2 17.31 Fe2+ catalysis of iodide and peroxodisulfate
Use the Fe2+/Fe3+ cycle to avoid the slow direct reaction between two negative ions: Fe2+ is oxidised, then Fe3+ oxidises iodide back to Fe2+.
How this is tested
- Write S2O8^2- plus Fe2+ and I- plus Fe3+ ionic equations for the catalytic cycle.
- Explain the high uncatalysed activation energy as repulsion between negative ions.
- State that Fe2+ works because it can be oxidised and then reduced again.