Antimony, Sb3+

 Most common oxidation states: +3, +5

 M.P. 630o

B.P. 1380o

Density 6.69 g/cm3

Characteristics: Brittle, silvery. Not very active, but reacts with oxygen, sulfur and chlorine at high temperatures.

 Characteristic reactions of Sb3+:

(Sb(III) is the more stable oxidation state.)

Chloride Ion:

No reaction observable, but will be present as SbCl4­.

Aqueous Ammonia:

Sb(III) reacts with aqueous ammonia to precipitate white Sb(OH)3.

Sb3+(aq) + 3NH3(aq) + 3H2O(l) <==> Sb(OH)3(s) + 3NH4+(aq) 

Sodium Hydroxide:

Sodium hydroxide also precipitates Sb(OH)3, which is amphoteric and dissolves in an excess of hydroxide and in acids.

Sb3+(aq) + 3OH­(aq) <==> Sb(OH)3(s)

Sb(OH)3(s) + OH­(aq) <==> Sb(OH)4­(aq)

Sb(OH)3(s) + 3H+(aq) <==> Sb3+(aq) + 3H2O(l) 

Hydrogen Sulfide:

Under moderately acidic conditions, H2S precipitates red Sb2S3.

2SbCl4­(aq) + 3H2S(aq) <==> Sb2S3(s) + 6H+(aq) + 8Cl­(aq)

This sulfide is soluble in solutions of hot NaOH which contain excess sulfide ion and in hot, concentrated (12 M) HCl.

Sb2S3(s) + 3S(aq) <==> 2SbS3(aq)

Sb2S3(s) + 6H+(aq) + 8Cl­(aq) <==> 2SbCl4­(aq) + 3H2S(aq)

Water:

Solutions of antimony(III) chloride in HCl react when added to excess water to form the basic, white, insoluble salt SbOCl.

SbCl4­(aq) + H2O(l) <==> SbOCl(s) + 2H+(aq) + 3Cl­(aq)

Reducing Agents:

In the presence of HCl, either aluminum or iron will reduce Sb3+ to Sb metal, which will be deposited as black particles.

SbCl4­(aq) + Al(s) <==> Sb(s) + Al3+(aq) + 4Cl­(aq)

No Reaction:

SO42-

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