JEE MAIN - Chemistry (2022 - 30th June Morning Shift - No. 14)
The reagent neutral ferric chloride is used to detect the presence of ______________
sulphide ion and alcoholic $$-$$OH group.
acetate ion and phenolic $$-$$OH group.
sulphide ion and phenolic $$-$$OH group.
acetate ion and alcoholic $$-$$OH group.
Explanation
Acetate ions gives deep red colour ppt on reaction with netural ferric chloride solution.
$6 \mathrm{CH}_{3} \mathrm{COO}^{-}+3 \mathrm{Fe}^{3+}+2 \mathrm{H}_{2} \mathrm{O} \longrightarrow {\left[\mathrm{Fe}_{3}(\mathrm{OH})_{2}\left(\mathrm{CH}_{3} \mathrm{COO}\right)_{6}\right]^{+} + 2 \mathrm{H}^{+}}$
${\left[\mathrm{Fe}_{3}(\mathrm{OH})_{2}\left(\mathrm{CH}_{3} \mathrm{COO}\right)_{6}\right]^{+} 4 \mathrm{H}_{2} \mathrm{O} \longrightarrow} \left.\left.\underset{\text{Brown red ppt}}{3\left[\mathrm{Fe}(\mathrm{OH})_{2}\left(\mathrm{CH}_{3} \mathrm{COO}\right)\right]}+3 \mathrm{CH}_{3} \mathrm{COOH}\right)_{2}\left(\mathrm{CH}_{3} \mathrm{COO}\right)_{6}\right]^{+}+2 \mathrm{H}^{+}$
Phenol reacts with freshly prepared ferric chloride solution and gives violet colour complex.
$$ 6 \mathrm{C}_{6} \mathrm{H}_{5} \mathrm{OH}+\mathrm{FeCl}_{3} \longrightarrow\underset{\text{Violet colour}}{\left[\mathrm{Fe}\left(\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{O}\right)_{6}\right]^{3-}}+3 \mathrm{HCl}+3 \mathrm{H}^{+} $$
$6 \mathrm{CH}_{3} \mathrm{COO}^{-}+3 \mathrm{Fe}^{3+}+2 \mathrm{H}_{2} \mathrm{O} \longrightarrow {\left[\mathrm{Fe}_{3}(\mathrm{OH})_{2}\left(\mathrm{CH}_{3} \mathrm{COO}\right)_{6}\right]^{+} + 2 \mathrm{H}^{+}}$
${\left[\mathrm{Fe}_{3}(\mathrm{OH})_{2}\left(\mathrm{CH}_{3} \mathrm{COO}\right)_{6}\right]^{+} 4 \mathrm{H}_{2} \mathrm{O} \longrightarrow} \left.\left.\underset{\text{Brown red ppt}}{3\left[\mathrm{Fe}(\mathrm{OH})_{2}\left(\mathrm{CH}_{3} \mathrm{COO}\right)\right]}+3 \mathrm{CH}_{3} \mathrm{COOH}\right)_{2}\left(\mathrm{CH}_{3} \mathrm{COO}\right)_{6}\right]^{+}+2 \mathrm{H}^{+}$
Phenol reacts with freshly prepared ferric chloride solution and gives violet colour complex.
$$ 6 \mathrm{C}_{6} \mathrm{H}_{5} \mathrm{OH}+\mathrm{FeCl}_{3} \longrightarrow\underset{\text{Violet colour}}{\left[\mathrm{Fe}\left(\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{O}\right)_{6}\right]^{3-}}+3 \mathrm{HCl}+3 \mathrm{H}^{+} $$
Comments (0)
