title: Iodine pentoxide
text: # Iodine pentoxide
  
  Iodine pentoxide is the chemical compound with the formula $I_2O_5.$ This iodine oxide is the anhydride of iodic acid, and the only stable oxide of iodine. It is produced by dehydrating iodic acid at 200 °C in a stream of dry air:
  
      $2HIO_3$ → $I_2O_5$ + $H_2O$
  
  ## Structure
  
  $I_2O_5$ is bent with an I–O–I angle of 139.2°, but the molecule has no mirror plane so its symmetry is $C_2$ rather than $C_{2v}.$ The terminal I–O distances are around 1.80 Å and the bridging I–O distances are around 1.95 Å.
  
  ## Reactions
  
  Iodine pentoxide easily oxidises carbon monoxide to carbon dioxide at room temperature:
  
      5 CO + $I_2O_5$ → $I_2$ + 5 $CO_2$
  
  This reaction can be used to analyze the concentration of CO in a gaseous sample.
  
  $I_2O_5$ forms iodyl salts, $[IO_2^+],$ with $SO_3$ and $S_2O_6F_2,$ but iodosyl salts, $[IO^+],$ with concentrated sulfuric acid.
  
  Iodine pentoxide decomposes to iodine (vapor) and oxygen when heated to about 350 °C.
  
  