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(i).An inorganic compound (A) is formed on passing a gas (B) through a concentrated liquor containing sodium sulphide and sodium sulphite. (ii) On adding (A) into a dilute solution of silver nitrate, a white precipitate appears which quickly changes into a black coloured compound (C). (iii) On adding two or three drops of ferric chloride into an excess of solution of (A), a violet coloured compound (D) is formed. But this colour disappears quickly. (iv) On adding a solution of (A) into the solution of cupric chloride, a white precipitate is first formed which dissolves on adding excess of (A) forming a compound (E). Identify (A) to (E) and give chemical equations for the reactions at steps (i) to (iv). |
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Answer» Solution :Let us summarize the given facts. (i) `Na_(2)SO_(3)+Na_(2)S+Gas(B)toA` (ii) `A+ AgNO_(3)toWhite ppt.tounderset(BLACK)(C)` (iii) `A+FeCl_(3)tounderset("Violet")(D)toDisappears` (iv) `A+CuCl_(2)White ppt.overset(excess of A)to ppt.underset(E)(dissolves)` The given set of reactions indicate that the compound is sodium thiosulphate which can be formed from equation (i) when the gas (B) is either `SO_(2)` or `l_(2)` and thus the various reactions can be written as below: (i) `Na_(2)SO_(3)+2Na_(2)S+underset(B)(3SO_(2))tounderset(A)(3Na_(2)S_(2)O_(2))` or `Na_(2)SO_(3)+Na_(2)S+underset(B)(I_(2))tounderset(A)(Na_(2)S_(2)O_(3))+2Nal` (ii) `Na_(2)S_(2)O_(3)+2AgNO_(3)tounderset(White ppt.)(Ag_(2)S_(2)O_(3))darr+2NaNO_(3)` `underset(C(Black))(Ag_(2)S_(2)O_(3)+H_(2)Odarr)+H_(2)SO_(4)` (iii) `underset((A))(3Na_(2)S_(2)O_(3))2FeCl_(3)tounderset("D(Violet)")(Fe_(2)(S_(2)O_(3)))+6NaCl` `2Fe^(3+)+2S_(2)O_(3)^(2-)to2Fe^(2+)+underset("Coloueless")(S_(4)O_(3)^(2-))` (iv) `underset((A))(2Na_(2)S_(2)O_(3))+2CuCl_(2)to2CuCI+Na_(2)S_(4)O_(6)+2NaCl` `2CuCl+Na_(2)S_(2)O_(3)tounderset(White)(Cu_(2)S_(2)O_(3))darr+2NaClxx3` `3Cu_(2)S_(2)O_(3)+2Na_(2)S_(2)O_(3)tounderset("Soluble complex(E)")(Na_(4)[Cu_(6)(S_(2)O_(3))_(9)]` |
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