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Compounds | Reactions | Production
Atomic: M.A.C. | Reference
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Reactions of Chromium
Reactions with water
Chromium metal does not react with water at room temperature.
Reactions with air
hromium metal does not react with air or oxygen at room temperature.
Reactions with halogens
Chromium reacts directly with fluorine at 400°C and 200-300 atmospheres to form chromium(VI) fluoride.
  Cr(s) + 3F2(g)CrF6(s)
Under less extreme conditions, chromium(V) fluoride is formed.
  2Cr(s) + 5F2(g)2CrF5(s)
Under milder conditions still, chromium metal reacts with the halogens to form chromium(III) trihalides.
  2Cr(s) + 3F2(g)2CrF3(s)
  2Cr(s) + 3Cl2(g)2CrCl3(s)
  2Cr(s) + 3Br2(g)2CrBr3(s)
  2Cr(s) + 3I2(g)2CrI3(s)
Reactions with acids
Chromium metal dissolves in dilute hydrochloric acid to form solutions containing the aquated Cr(II) ion together with hydrogen gas.
  Cr(s) + 2HCl(aq)Cr2+(aq) + 2Cl-(aq) + H2(g)
Similar results are seen for sulphuric acid but pure samples of chromium may be resistant to attack. Chromium metal does not react with nitric acid.
 
Reduction Potentials
Balanced half-reaction E0 / V
Cr3+ + e-Cr2+ -0.408
Cr3+ + 3e-Cr(s) -0.744
Cr2+ + 2e-Cr(s) -0.91
Cr2O72- + 14H+ + 6e-2Cr3+ + 7H2O +1.33
Cr2O72- + 12H+ + 6e-2CrOH2+ + 5H2O +1.26
Cr2O72- + 10H+ + 6e-2Cr(OH)2+ + 3H2O +1.14
Cr2O72- + 14H+ + 12e-2Cr(s) + 7H2O +0.29
HCrO4- + 7H+ + 3e-Cr3+ + 4H2O +1.20
CrO42- + 4H2O + 3e-Cr(OH)3(s) + 5OH- -0.13
HCrO4- + 6H+ + 3e-CrOH2+ + 3H2O +1.28
CrO42- + 7H+ + 3e-CrOH2+ + 3H2O +1.40
CrO42- + 6H+ + 3e-Cr(OH)2+ + 2H2O +1.28
CrO42- + 4H+ + 3e-CrO2- + 2H2O +0.95
CrO42- + 2H+ + 3e-CrO33- + H2O +0.36