JEE MAIN - Chemistry (2023 - 11th April Morning Shift - No. 8)
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 $$\mathrm{FeCl}_{3}$$, it gave deep red colour which disppeared on boiling and a brown red ppt was formed. The mixture contains :
SO$$_3^{2-}$$ & C$$_2$$O$$_4^{2-}$$
$$\mathrm{CH}_{3} \mathrm{COO}^{-} \& ~\mathrm{NO}_{3}^{-}$$
$$\mathrm{C}_{2} \mathrm{O}_{4}{ }^{2-} \& ~\mathrm{NO}_{3}^{-}$$
$$\mathrm{SO}_{3}^{2-} \& ~\mathrm{CH}_{3} \mathrm{COO}^{-}$$
Explanation
The mixture of salts gives a dark brown ring when treated with ferrous sulphate in acidic medium. This is a characteristic reaction of nitrate ions (NO$_3^-$). The brown ring is due to the formation of a complex between NO and Fe$^{2+}$.
Additionally, the mixture gives a deep red color when treated with neutral ferric chloride (FeCl$_3$), which then disappears upon boiling to form a red-brown precipitate. This is a classic reaction of acetate ions (CH$_3$COO$^-$) with Fe$^{3+}$. Initially, the acetate ions form a complex with ferric ions, leading to the deep red color. Upon boiling, hydroxide ions displace some acetate ions in the complex, resulting in the red-brown precipitate.
Therefore, the mixture contains acetate (CH$_3$COO$^-$) and nitrate (NO$_3^-$) ions.
Additionally, the mixture gives a deep red color when treated with neutral ferric chloride (FeCl$_3$), which then disappears upon boiling to form a red-brown precipitate. This is a classic reaction of acetate ions (CH$_3$COO$^-$) with Fe$^{3+}$. Initially, the acetate ions form a complex with ferric ions, leading to the deep red color. Upon boiling, hydroxide ions displace some acetate ions in the complex, resulting in the red-brown precipitate.
Therefore, the mixture contains acetate (CH$_3$COO$^-$) and nitrate (NO$_3^-$) ions.
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