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Awhite substance Areactswithdilute H_(2)SO_(4) isproduce acolourless B and acidified K_(2)Cr_(2)O_(7) solutionproduces a greensolutionand a slighlycolouredprecipitate D .Thesubstance B toburnsin airtoproducea gas Ewhich reactswith B ito yiedD and a colouless liquid .Anhyhdrous coppersulphateis turned blue on additionof thiscolourlessliquid additionod aqueous NH_(3) or NaOHto Cproducefirsta precipitatewhichdissolve in theexcess of the respective reagenttoproduce a clearsolutionin eachcaseidentify A,B,C, and E. Writetheequationof thereactioninvolved. |
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Answer» Solution :`A = ZnS,B = H_(2)S ,C = ZnSO_(4),D =- S , E = SO_(2)` A white substance A reactswith dilute `H_(2)SO_(4)` to produce a colourless gas .B and a colourless solution C .The reactionbetween B and acidified `K_(2)Cr_(2)O_(7)` solution produces a green solutionand a slightlycoloured precipitate D.Thisprecipitatemust be sul,phate , so gas B must be hydrogensulphide ,Sulpbuur in airto produce a gas sulphur dioxidewhich reactswithhydrogen sulphide to yield sulphuragainand a colourless LIQUID water .Anhydrous coppersulphateis turnedblue on addition of water a precipitatewhichdissolve a clearsolutionin excesssolutionof therespectiveregaoin to produce a clearsolutionin eachcase .Thissuggesist that Cmust be sulphateofeitherzine oraluminium so, A may be zine sulphide . `ZnS +H_(2)SO_(4) rarr H_(2)S + ZnSO_(4)` `Cr_(2)O_(7)^(2-) + 4H^(o+) ("From" H_(2)SO_(4)) + 3H_(2)S rarrunderset("Green solution")(2Cr^(3+)) +7H_(2)O +3S darr` `S + SO_(2) rarr SO_(2)` `SO_(2) +2H_(2)S rarr 2H_(2)O +3S` `ZnSO_(4) +2NaOH rarr underset("White")(Zn(OH)_(2)darr) +Na_(2)SO_(4)` `Zn(OH)_(2) +2NaOH rarr Na_(2)ZnO_(2) +2H_(2)O` |
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