Replacement of copper with iron powder

1) Excess acid in the copper solution consumes iron and then gives off hydrogen

    Fe + 2H+ ——  Fe2+ + H2

2) The hydrogen dissolved in the copper solution makes the ferric ions generated by the replacement reaction continue to be oxidized to ferric ions, and the ferric ions with strong oxidizing ability are reduced to ferric ions by iron powder, so a part of iron is consumed

 

    4H+  +  4Fe2+ + O2 ——  4Fe3+ + H2O

    2Fe3+  + Fe —— 3Fe2+

3) Fe3+ can also oxidize the already formed Cu to Cu2+, thus increasing the consumption of iron

    2Fe3+  + Cu ——  2Fe2+ + Cu2+