Question

A colloid is formed by adding $FeC{l}_3$ in excess of hot water. What will happen if excess sodium chloride is added to this colloid?

Answer 1

• When $FeC{l}_3$ is added to excess of hot water, a positively charged sol of hydrated ferric oxide is formed due to adsorption of $F{e}^{3+}$ ions.
• On adding excess of $NaCl$, negatively charged chloride ions coagulate the positively charged sol of hydrated ferric oxide.