JEE Main 2022 — Surface Chemistry Question with Solution

Lyophilic colloids are stable due to charge and solvation, they can be used to protect Lyophobic colloids

Emulsions are liquid-liquid type of colloids

If ${\mathrm{FeCl}}_3$ is added to the excess of hot water, a positively charged sol of hydrated ferric oxide is formed due to adsorption of ${\mathrm{Fe}}^{3+}$ ions. However, when ferric chloride is added to $\mathrm{NaOH}$ solution, a negatively charged sol is obtained with adsorption of ${\mathrm{OH}}^{-}$ ions.

${\mathrm{Fe}}_2{\mathrm{O}}_3·{\mathrm{xH}}_2\mathrm{O}/{\mathrm{Fe}}^{3+}$
Positively charged

$\mathrm{Fe}{\left(\mathrm{OH}\right)}_3/{\mathrm{OH}}^{-}$
Negatively charged