Question

Which mixture of the solutions will lead to the formation of negatively charged colloidal $\left[AgI\right]I^{-}$sol. ?

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Answer 1

Generally charge present on the colloid is due to adsorption of common ion from dispersion medium. Millimole of KI is maximum in option (d).

$\text{Milli moles of}AgN{O}_3=50\times 1=50$
$\text{Milli moles of}KI=50\times 2=100$
$KI$ is in excess.

$AgN{O}_3\left(aq\right)+KI\left(aq\right)\to AgI\left(s\right)\downarrow +AgN{O}_3\left(aq\right)$

$AgI$ gets precipitated.
The precipitated silver iodide adsorbs iodide ions $\left(I^{-}\right)$ from the dispersion medium and negatively charged colloidal sol is formed $AgI/I^{-}$

Hence, option (d) is correct.