JEE Main · 2023 · 11 Apr 2023 · Shift 1 · Practical and Analytical Chemistry

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When a solution of mixture having two inorganic salts was treated with freshly prepared ferrous sulphate in acidic medium, a dark brown ring was formed whereas on treatment with neutral

FeCl_{3}

, it gave deep red colour which disappeared on boiling and a brown red ppt was formed. The mixture contains

(A) $CH_{3} COO^{-}$ & $NO_{3}^{-}$ ✓ Correct
(B) $C_{2} O_{4}^{2 -}$ & $NO_{3}^{-}$
(C) $SO_{3}^{2 -}$ & $CH_{3} COO^{-}$
(D) $SO_{3}^{2 -}$ & $C_{2} O_{4}^{2 -}$

Answer: (A)

Solution

The brown ring test with freshly prepared

FeSO X_{4}

in acidic medium is characteristic of nitrate ions (

NO X_{3} X^{-}

). The reaction forms

[Fe (H X_{2} O) X_{5} (NO)] X^{2 +}

, which appears as a brown ring. The deep red color with neutral

FeCl X_{3}

that disappears on boiling to give a brown-red precipitate is characteristic of acetate ions (

CH X_{3} COO X^{-}

). Acetate forms a blood-red complex

[Fe X_{3} (OH) X_{2} (CH X_{3} COO) X_{6}] X^{+}

with

Fe X^{3 +}

, which decomposes on heating to give

Fe (OH) X_{2} (CH X_{3} COO)

as a red-brown precipitate. Therefore, the mixture contains

CH X_{3} COO X^{-}

and

NO X_{3} X^{-}

JEE Main · 2023 · 11 Apr 2023 · Shift 1 · Single correct option

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JEE Main · 2023 · 11 Apr 2023 · Shift 1 · Practical and Analytical Chemistry

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