Hydrogen Sulphide : It is prepared in the laboratory by the action of dil.
H2SO4 on ferrous sulphide in kipp’s apparatus, FeS + H2SO4 —> FeSO4 + H2S
. It is colourless gas having foul smell resembling that of rotten eggs. It reacts with many cations (of group II and IV) to give coloured sulphides,
Cu+2 + S–2 —> CuS; Cd+2 + S–2 —> CdS
;
Black (Yellow)
Ni+2 + S–2 —> NiS; Co+2 + S–2 —> CoS
;
Black (Yellow)
The solubility of sulphides can be controlled by the H+
ions concentration and therefore, H2S
finds extensive use in qualitative analysis of cation radicals.
Oxides of sulphur : Sulphur forms several oxides of which sulphur dioxide
(SO2) and sulphur trioxide
(SO3) are most important.
(i) Sulphur dioxide (SO2) :It is prepared by burning sulphur or iron pyrites in air.
S8 + 2O2 —> 8SO2; 4Se2 + 11O2 —> 2FeO3 + 8SO2
In laboratory, it is prepared by heating copper turnings with conc. H2SO4
Cu + 2H2SO4 —> CuSO4 + SO2 + 2H2O
It is a colourless gas with irritating and suffocating smell.
hybridized.
(ii) Sulphur trioxide (SO3): It is formed by the oxidation of SO2.
2SO2 + O2 ———————> 2SO3
In the gaseous phase, it exists as planar triangular moleculear species involving hybridization of the S-atom. Itt has three S—O σ bonds and three S–O π bonds. The O–S–O bond angle is of 120o.
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