Question

Why is ferric hydroxide colloid positively charged when prepared by adding ferric chloride to hot water?

• A. Due to precipitation of ferric hydroxide there is an excess of $F{e}^{3+}$ ions.
• B. Due to preferential adsorption of $F{e}^{3+}$ ions by the sol of $Fe(OH{)}_{3.}$
• C. Due to absence of any negatively charged ion.
• D. Due to adsorption of $O{H}^{-}$ and $C{I}^{-}$ ions, the remaining sol has only $F{e}^{3+}$ ions.

Answer 1

The correct option is B Due to preferential adsorption of $F{e}^{3+}$ ions by the sol of $Fe(OH{)}_{3.}$

The adsorption of positively charged Fe3+ ions by the sol of hydrated ferric oxide results in positively charged colloid.