A white solid A reacts with dilute H_(2)SO_(4) to produce a colourless gas B and a colourless solution C. the reaction between B and acidified dichromate yields a green solution and a slightly coloured precipitate D. the substance D, when burnt in air, gives a gas E which reactswith B to yield D and a colourlesss liquid. anhydrous copper sulphate turns blue with this colourless liquid. the addition of aqueous NH_(3) or NaOH toC produces a precipitate that dissolves in an excess of the reagent to form a clear solution. Q. Which of the following reactions are relevant to the action of NH_(3) or NaOH solution on C?

A white solid A reacts with dilute H_(2)SO_(4) to produce a colourless

1.	A white solid A reacts with dilute H_(2)SO_(4) to produce a colourless gas B and a colourless solution C. the reaction between B and acidified dichromate yields a green solution and a slightly coloured precipitate D. the substance D, when burnt in air, gives a gas E which reactswith B to yield D and a colourlesss liquid. anhydrous copper sulphate turns blue with this colourless liquid. the addition of aqueous NH_(3) or NaOH toC produces a precipitate that dissolves in an excess of the reagent to form a clear solution. Q. Which of the following reactions are relevant to the action of NH_(3) or NaOH solution on C?
Answer» `Zn(OH)_(2)+4NH_(3) to [Zn(NH_(3))_(4)]^(2+)+2OH^(-)` `Zn(OH)_(2)+2OH^(-) to [Zn(OH)_(4)]^(2-)` `Pb(OH)_(2) to 4NH_(3) to [Pb(NH_(3))_(4)]^(2+)+2OH^(-)` `Pb(OH)_(2)+2OH^(-) to [Pb(OH)_(4)]^(2-)` SOLUTION :One of the three colourless gases `-CO_(2),SO_(2) and H_(2)S`- is generally produced by the action of dilute `H_(2)SO_(4)` on a salt. As the gas turns acidified dichromate solution green along with the formation of SLIGHTLY coloured precipitate (may be S), the gas seems to be `H_(2)S` and so the substance A seems to be a sulphide. again, the action of `NH_(3)` or an NaOH solution on the solution of the substance in dilute `H_(2)SO_(4)` suggets that the substance is a zinc salt. thus, A is most likely ZNS. let us go through the REACTIONS now.