| Reactions of Arsenic |
 Reactions with water |
| Arsenic does not react with water in the absence of air under normal conditions. |
| Reactions with air |
| Arsenic is stable in dry air, but the surface oxidizes slowly in moist air to give a bronze tarnish and finally a black covering.
When heated in air, arsenic ignites "arsenic trioxide" - actually tetra-arsenic hexaoxide, As4O6. This is accompanied by phosphorescence under some conditions. When heated in oxygen, arsenic ignites to form "arsenic pentoxide" - actually tetra-arsenic decaoxide.
|
4As(s) + 5O2(g) As4O10(s) |
| 4As(s) + 3O2(g)As4O6(s) |
| Reactions with halogens |
| Arsenic reacts with fluorine to form the gas arsenic(V) fluoride.
|
| 2As(s) + 5F2(g)2AsF5(g) |
| Arsenic reacts under controlled conditions with the halogens fluorine, chlorine, bromine and iodine to form arsenic(III) trihalides.
|
| 2As(s) + 3F2(g)2AsF3(l) |
| 2As(s) + 3Cl2(g)2AsCl3(l) |
| 2As(s) + 3Br2(g)2AsBr3(l) |
| 2As(s) + 3I2(g)2AsI3(l) |
| Reduction Potentials |
| Balanced half-reaction |
E0 / V
|
H3AsO4 + 3H+ + 2e- AsO+ + 3H2O
|
+0.55 |
| H3AsO4 + 2H+ + 2e-H3AsO3 + H2O
|
+0.559 |
| H3AsO4 + 2H+ + 2e-H3AsO3 + H2O
|
+0.577 |
| H3AsO4 + 2H+ + 2e-H3AsO3 + H2O
|
+0.577 |
| H3AsO4- + 3H+ + 2e-H3AsO3 + H2O
|
+0.666 |
| H3AsO42- + 4H+ + 2e-H3AsO3 + H2O
|
+0.881 |
| HAsO42- + 3H+ + 2e-H3AsO3- + H2O
|
+0.609 |
| AsO43- + 3H2O + 2e-H3AsO3- + 4OH- |
-0.67 |
| 2H3AsO4 + 4H+ + 4e-As2O3(s) + 5H2O
|
+0.58 |
| 2H2AsO4- + 6H+ + 4e-As2O3(s) + 5H2O
|
+0.687 |
| 2HAsO42- + 8H+ + 4e-As2O3(s) + 5H2O
|
+0.901 |
| 2AsO43- + 10H+ + 4e-As2O3(s) + 5H2O
|
+1.27 |
| AsO43- + 8H+ + 5e-As(s) + 4H2O
|
+0.648 |
| As2O3(s) + 6H+ + 6e-2As(s) + 3H2O
|
+0.234 |
| AsO+ + 2H+ + 3e-As(s) + H2O
|
+0.254 |
| H3AsO3 + 3H+ + 3e-As(s) + 3H2O
|
+0.248 |
| H2AsO3- + 4H+ + 3e-As(s) + 3H2O
|
+0.429 |
| H2AsO3- + H2O + 3e-As(s) + 4OH- |
-0.68 |
| As(s) + 3H+ + 3e-AsH3(g) |
-0.608 |
