title: Potassium hypochromate
text: # Potassium hypochromate
  
  Potassium hypochromate is a chemical compound with the formula $K_3CrO_4$ with the unusual $Cr^{5+}$ ion. This compound is unstable in water but stable in alkaline solution and was found to have a similar crystal structure to potassium hypomanganate.
  
  ## Preparation
  
  This compound is commonly prepared by reacting chromium(III) oxide and potassium hydroxide at 850 °C under argon:
  
      $Cr_2O_3$ + 6 KOH → 2 $K_3CrO_4$ + $H_2O$ + 2 $H_2$
  
  This compound can be prepared other ways such as replacing chromium oxide with potassium chromate. It is important that there is no $Fe^{2+}$ ions present because it would reduce the Cr(V) ions to Cr(III) ions.
  
  ## Reactions
  
  Potassium hypochromate decomposes in water to form chromium(III) oxide and potassium chromate when alkali is not present or low. Potassium hypochromate also reacts with acids such as hydrochloric acid to form chromium(III) oxide, potassium chromate, and potassium chloride:
  
      6 $K_3CrO_4$ + 10 HCl → 4 $K_2CrO_4$ + $Cr_2O_3$ + 5 $H_2O$ + 10 KCl
  
  Other reducing agents such as hydroperoxides can reduce the hypochromate ion into chromate ions. At extremely high temperatures, it decomposes into potassium chromate and potassium metal.
  
  This compound is used to synthesize various compounds such as chromyl chlorosulfate by reacting this compound with chlorosulfuric acid.
  
  