question_answer

A reddish brown sol is obtained by adding small quantity of \[FeC{{l}_{3}}\]solution to freshly prepared and well washed \[Fe{{(OH)}_{3}}\] ppt. fixed layer and mobile layer are represented as

A) \[\left[ FeC{{l}_{3}} \right]F{{e}^{3+}}\]                      \[O{{H}^{-}}\]

B) \[\left[ Fe{{(OH)}_{3}} \right]F{{e}^{3+}}\]      \[C{{I}^{-}}\]

C) \[\left[ Fe{{(OH)}_{3}} \right]F{{e}^{3+}}\]      \[3C{{I}^{-}}\]

D) \[\left[ FeC{{l}_{3}} \right]F{{e}^{3+}}\]                      \[3O{{H}^{-}}\]

Correct Answer: C

Solution :

[c] \[Fe{{(OH)}_{3}}\] Sol adsorbs common ion of \[FeC{{l}_{3}}\] and \[Fe{{(OH)}_{3}}\] from \[FeC{{l}_{3}}\], i.e. \[F{{e}^{3+}}\]and positively charged sol is the fixe part of the electrical double layer. Thus, \[C{{I}^{-}}\](to balance charge of \[F{{e}^{3+}}\]) ions are on the mobile part of the electrical double layer.