The nature of charge on resulting colloidal particles when ${\mathrm{FeCl}}_3$ is added to excess of hot water is:

If ${\mathrm{FeCl}}_3$ is added to hot water, a positively charged sol, hydrated ferric oxide is formed due to adsorption of ${\mathrm{Fe}}^{3+}$ ions.

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

Positively charged.

Thus, When${\mathrm{FeCl}}_3$​ sol is treated with hot water, it forms $\mathrm{Fe}{\left(\mathrm{OH}\right)}_3$ forming ${\mathrm{Fe}}^{3+}$ ions(in excess amount) and these positive ions are adsorbed preferentially.