The metallic salt `(XY)` is soluble in water.
(a) When the aqueous soluble of `(XY)` is treated with `NaOH` solution, a white precipitate `(A)` is formed. In excess of `NaOH` solution, a white precipitate `(A)` is formed. In excess of `NaOH` solution, white precipitate `(A)` dissolves to form a compound `(B)`. When this solution is boiled with soild `NH_(4) Cl`, a precipitate of compound `(C)` is formed.
(b) An aqueous solution on treatment with `BaCl_(2)` solution gives a white precipitate `(D)` white is insoluble in conc `HCl`.
( c) The metallic salt `(XY)` forms a double salt `(E)` with potassium sulphate.
Identify `(XY),(A),(B),(C),(D)` and `(E)`.

Explanation

(a)
`(X) is Al^(3+) ion`
`Al_((aq))^(3+) + 3NaOH_((aq)) rarr underset(underset((A))"White ppt.") ((Al(OH)_(3))darr 3 Na^(oplus))`
`Al(OH)_(3) + underset("Excess") (NaOH_((aq))) overset("Heat") rarr underset(underset(underset("aluminate") ("Sodium meta-"))((B))) (NaAlO_(2)) + 2H_(2) O`
`NaAlO_(2) + NH_(4)Cl + H_(2) O overset("Heat") rarr underset(underset(underset("hydroxide") ("Aluminium"))((C))) (Al(OH)_(3)darr) + NaCl + NH_(3)`
The metallic salt `(XY)` on treatment with `NaOH` solution, gives a while precipitate of aluminium hydroxide, `Al(OH)_(3). Al(OH)_(3)` dissolves in excess of `NaOH` solution forming sodium metaluminate, `NaAlO_(2) . NaAlO_(2)` on boiling with `NH_(4) Cl` solution gives with precipitate of aluminium hydroxide, `Al(OH)_(3)`.
(b) `(XY)_((aq)) overset("BaCl_(2) solution")rarr underset("White ppt.") ((D)) overset("conc HCl") rarr underset("Insoluble")((D))`
`(Y)` is `SO_(4)^(2-)` ion.
`So_(4(aq))^(2-)+ Ba_((aq))^(2+) rarr underset("White ppt.") (BaSO_(4) darr)`
`(D)` is barium sulphate, `BaSO_(4)`, which is insoluble in conc `HCl`.
Hence, the salt `(XY)` is `Al_(2)(SO_(4))_(3)`, aluminium sulphate.
( c) The double salt `(E)` formed by `(XY)` with potassium sulphate is `K_(2) SO_(4) .Al_(2) (SO_(4))_(3). 24 H_(2) O` i.e. potash alum.
Hence, `(XY)` is `Al_(2)(SO_(4))_(3) , (A)` is `Al(OH)_(3) , (B)` is `NaAlO_(2) , ( C)` is `Al(OH)_(3) , (D)` is `BaSO_(4)` and `(E)` is `K_(2) SO_(4). Al_(2) (SO_(4))_(3) .24 H_(2) O`.