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Reactions of Iridium
Reactions with water
Iridium does not react with water under normal conditions.
Reactions with air
Iridium is largely immune to atmospheric attack. On heating with oxygen, iridium metal forms iridium (IV) oxide.
  Ir(s) + O2(g)IrO2(s)
Reactions with halogens
Iridium reacts directly with fluorine to form the highly corrosive iridium(VI) fluoride. This material, with care, can be heated to form iridium(V) fluoride, which has the structure [IrF5]4.
  Ir(s) + 3F2(g)IrF6(s)
The trihalides iridium(III) fluoride, iridium(III) chloride, iridium(III) bromide and iridium(III) iodide can be formed through the direct reaction of the metal with the halogen under anhydrous (dry) conditions.
  2Ir(s) + 3F2(g)2IrF3(s)
  2Ir(s) + 3Cl2(g)2IrCl3(s)
  2Ir(s) + 3Br2(g)2IrBr3(s)
  2Ir(s) + 3I2(g)2IrI3(s)
Reactions with acids
Iridium metal is notably inert to reaction with acids, including aqua regia (a mixture of hydrochloric acid and nitric acid known for its ability to dissolve gold metal).
Reduction Potentials
Balanced half-reaction E0 / V
Ir3+ + 3e-Ir(s) +1.15
IrCl62- + e-IrCl63- +1.026
IrCl62- + 4e-Ir(s) + 6Cl- +0.835
IrCl63- + 3e-Ir(s) + 6Cl- +0.77
IrO2(s) + 4H+ + 4e-Ir(s) + H2O +0.93
IrO2(s) + 2H2O + 4e-Ir(s) + 4OH- +0.1
Ir2O3 + 3H2O + 6e-2Ir(s) + 6OH- +0.1