| 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 |