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# Which of the following is a positively charged sol ?

$(a)\;Cds\qquad(b)\;As_{2}S_{3}\qquad(c)\;gelatin\qquad(d)\;Metal\;Hydroxides\;like\;Fe(OH)_{3}\;,Al(OH)_{3}\;,etc$

Answer : $Metal\;hydroxides\;like\;Fe(OH)_{3}\;,Al(OH)_{3}\;,etc$
Explanation :
In a colloidal solution , the ion which is common with their own lattice ions is preferentially adsorbed . If AgI solution is added to an aqueous solution of potassium Iodide , the precipitated silver iodide will adsorb negative ions (common ions) from the dispersion medium to form a negatively charged sol .
$AgI : I^{-}\;$ and if KI is added to $\;AgNO_{3}\;$ the sol will be positively charged sol & $\;Fe(OH)_{3}\;$ & other metal hydroxides are positively charged sol .