JEE Main 2023 — Salt Analysis Question with Solution

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.