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(i) An aqueous solution of a compound A ...

(i) An aqueous solution of a compound A is acidic towards litmus and A sublimes at about `300^(@)C`
(ii) A solution of A, on treatment with an excess of `NH_(4)SCN`, gives a red compound, and on treatment with a solution of `K_(4)[Fe(CN)_(6)]`, gives a blue compound.
(iii) The solid A, on being heated with an excess of `K_(2)Cr_(2)O_(7)` in the presence of concentrated `H_(2)SO_(4)`, evolves deep red vapours of D.
(iv) On passing the vapours of D into a solution of NaOH and then adding the solution of acetic acid and lead acetate, a yellow precipitate of a compound E is obtained.
Q. Which is the oxidation state of the central atom in vapour D?

Text Solution

Verified by Experts

The correct Answer is:
A=`FeCl_(3)`, B=`Fe(SCN)_(3)` , C=`Fe_(4)[Fe(CN)_(6)]_(3)` , D=`CrO_(2)Cl_(2)` , E=`PbCrO_(4)`
(i)`FeCl_(3)+3H_(2)O to Fe(OH)_(3)darr` (reddish brown) +`3HCl`,so solution is acidic in nature.
(ii)`Fe^(3+) +3SCN^(-) to Fe(SCN)_(3)` (red colouration)
`4Fe^(3+) +3[Fe(CN)_(6)]^(4-) toFe_(4)[Fe(CN)_(6)]_(3)`(Prussian blue).
(iii)`Cr_(2)O_(7)^(2-)+4Cl^(-) 6H^(+) to 2CrO_(2)Cl_(2) uarr` (deep red) +`3H_(2)O`
(iv)`CrO_(2)Cl_(2)uarr+4OH^(-)toCrO_(4)^(2-) + 2Cl^(-)+2H_(2)O`
`Pb^(2+) +CrO_(4)^(2-) to PbCrO_(4) darr` (yellow)
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