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Compounds | Reactions | Production
Atomic: M.A.C. | Reference
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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