Question

At the interaction of AgNO₃ and K₂CrO₄ solutions a sol of Ag₂CrO₄ with negatively charged grains is formed. Determine, which electrolyte is taken in excess at its obtaining and write down the scheme of micelle structure of this sol. Arrange in row of increasing of coagulation thresholds the following electrolytes: MgSO₄, Al(NO₃)₃ and K₄[Fe(CN)₆] in relation to this sol.

Answer 1

The charge on the colloidal particles upon the preferential adsorption of the ions from the electrolyte that are common with their own littice ions. When $AgNO_{3}$ is added to an aqueous solution of $Kl$ , the yellow precipitate of $AgI$ adsorb $I^-$ ions from the electrolyete KI and forms negatively charged colloidal particles.

$AgI+KI$ to $[AgI]I^{-}$ : $NO_{3}^{-}$

When formed on adding kI solution to an aqueous solution of $AgNO_{3}$

Positively charged $Ag^{+}$ ions are adsorbed from the electrolyte and the collouidal particles acquire negative charge.