This is because, the powerful oxidizing agent permanganate ion has oxidized the sulfide ion (-2) to zero oxidation state. When H2S is bubbled through acidified KMnO4 solution, it decolorises and a white turbidity is observed.The reaction can be viewed as the reverse of a disproportionation reaction.
What happens is, the S atom in sulphite/bisulphite (Oxidation state +4) and in H2S (Oxidation state -2) have coproportionated to give molecular sulfur in zero oxidation state. When H2S is bubbled through a solution of Sodium sulphite or Sodium bisulphite, a white turbidity of sulfur is seen.The following two points do not fall in place here, kindly arrange them wherever they are best fit: (CH 3COO) 2Pb + H 2S -> PbS + 2(CH 3COOH) It is prepared by dipping a filter paper for some time in Lead acetate solution.If the salt in question is a sulphide an acrid smell of rotten eggs will be observed and the lead ethanoate will turn black, due to formation of solid black Lead sulfide powder. If the substance is soluble use lead acetate solution, if solid add dilute hydrochloric acid and test the gas with lead ethanoate paper. If a sulfide solution is reacted with silver nitrate, it forms a black precipitate of Ag 2S. 4- complex anion formed in the presence of sulphide ions is the cause for this coloration, colouration is important. In the presence of sulphide ions a deep violet coloration is formed. Sulphides Sodium Nitroprusside test for anions
3.2.1 Note on the tetracyano complex of copper.
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