A mixture of two salt was treated as follows :
i. The mixture was heated with magnanese dioxide and concentrated sulphuric acid , when a yellowish -green gas was liberated.
ii. The mixture on heating with sodium hydroxide solution gave a gas which turned red litmus blue
iii. Its solution in water gave a blue precipitate with potassium ferricyanide and red colourtion with ammonium thiocynate
iv. The mixture was boiled with potassium hydroxide and the librated gas was bubbled through an alkline solution of `K_(2)HgI_(4)` to give a brown precipitate identify the two salts gives ionic equation for the reaction involved in the tests (i) , (ii) and (iii).

Explanation

(i) `2Cl^(-)+MnO_(2)+H_(2)SO_(4)(conc.)+2h^(+)toMnSO_(4)+underset(groon)underset(Yellow wish)(Cl_(2)uarr)+2H_(2)O`
(ii) `NH_(4)^(+)+2NaOHtoNH_(3)+H_(2)O+Na^(+)`
(iii) `3Fe^(2+)+2[Fe(CN)_(6)]^(3-)toFe_(3)underset((blue ppt.))underset(Prussian blue)([Fe(CN_(6))]_(2))` (i) `Mixture+MnO_(2)+H_(2)SO_(4)(conc.)to` yellowish green gas M
The reaction suggests thal the mixture contains `Cl^(-)` ions.
`therefore 2Cl^(-)+MnO_(2)+H_(2)SO_(4)(conc.)+2H^(+)MnSO_(4)+underset(Yellowwish green)(CI_(2)uarr)+2H_(2)O`
(ii) `Mixture+NaOHto` Gas turningred litmus blue
The reaction suggests that the gas is ammonia (ie, basic in character turning red litmus blue). Ammonia will be evolved from an ammonium salt. Thus,
`NH_(4)^(+)+NaOHtoNH_(3)+H_(2)O+Na^(+)`
(iii) Solution of mixture `+K_(2)[Fe(CN)_(6)] toblue ppt`.
The reaction suggests that the mixture contains a Fe (II) of prussian blue complex.
`3Fe^(2+)+2[Fe(CN)_(6)]^(3+)Fe_(3)underset((Blue ppt.))underset(Prussian blue) ([Fe(CN)_(6)]_(2))`
Red colourless with ammonium thioyanate suggests that some Fe (III) is also present. It is likely that a part of Fe (II) is oxidized (III) by air.
`Fe^(3+)+3NH_(4)SCN toFeunderset(“red colourless”)((SCN))+3NH_(4)^(+)`
`2Fe^(2+)+[O]+2H^(+)to 2Fe^(3+)+H _(2)O`
(iv) `Mixture+KOHtoGasoverset(K_(2)Hgl_(4))tobrown ppt`.
the above reaction can be explained, when ammonia is liberated on boiling the mixture with potassium hydroxide. The liberated ammonia reacts with an alkaline solutions of `K_(2)Hgl_(4)` Hgle to giv a brown ppt.
Hence, the mixture contains, `Fe^(2+)`,`NH_(4)^(+)` and cr ions (with an impurity of `Fe^(3+)` ions).
The two salts are `FeCl_(2)` and `NH_(4)CI`.