A hydrated mettalic salt(A). Light green in colour , on careful heating gives a white anhydrates residue (B),(B) is soluble in water and its aqueous gives a dark blue precipitate ( C ) with potassium hexacyanidoferrate (III) . (B ) on strong heating gives a brown residue(D) and a mixture of two gases(E ) and (F ). The gaseous mixture when passed through acidified potassium dichromate , produce green colour solution and when passed through lead acetate solution gave a white precipitate. Out of two gase( E) can act as both reducing as well as oxidising agent.
Identify (A) ,(B) ,(C ),(D) , and (F) and gives the reaction involved.
Explain why salt(A) become white on heating .

Answer

(a) `FeSO_(4).7H_(2)O("green") to FeSO_(4)+7H_(2)O`
`Fe^(2+)(aq)+3[Fe(CN)_(6)]^(3-)(aq) to Fe^(3+)(aq) +Fe(CN)_(6)^(4-)(aq)`
`4Fe^(3+)(aq)+3[Fe(CN)_(6)]^(4-) (aq) to Fe_(4)[Fe(CN)_(6))_(3)] downarrow("Turnbull's blue" -(C ))`
`2FeSO_(4)underset("strong")overset(Delta)toFe_(2)O_(3)+SO_(2)uparrow +SO_(3)uparrow`
(B),(D),(E ) ,(F)
`3SO_(2)+Cr_(2)O_(7)^(2-)+2H^(+)("green solution")+3SO_(4)^(2-)+H_(2)O`
(E)
`SO_(3)+H_(2)O to H_(2)SO_(4)`
`pb^(2+)+SO_(4)^(2-) to PbSO_(4) downarrow("white")`