Question

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

• A. (a) Due to precipitations of ferric hydroxide there is an excess of $\mathrm { Fe } ^ { 3 + }$ions.
• A. (b) Due to preferential adsorptions of $\mathrm { Fe } ^ { 3 + }$ ions by the sol of $\mathrm { Fe } ( \mathrm { OH } ) _ { 3 }$.
• A. (c) Due to absence of absence of any negatively charged ion.
• A. (d) Due to adsorption of $\mathrm { OH } ^ { - }$ and $\mathrm { Cl } ^ { - }$ ions, the remaining sol has only $\mathrm { Fe } ^ { 3 + }$ions.

Answer 1

(b)

Sol. The adsorption of positively charged $\mathrm { Fe } ^ { 3 + }$ions by the sol of hydrated ferric oxide results in positively charged colloid.