Which mixture of the solutions will lead to the formation of negatively charged colloidal `[Agl]^(-)` sol. ?

Options

A. 50 mL of 0.1 M `AgNO_3` + 50 mL of 0.1 M KI
B. 50 mL of 1 M `AgNO_3` + 50 mL of 1.5 M KI
C. 50 mL of 1 M `AgNO_3` + 50 mL 2 M KI
D. 50 mL of 2 M `AgNO_3` + 50 mL of 1.5 M KI

Explanation

When KI is in excess, the I-ions are preferentially adsorbed by AgI to form `[AgI]I^(-)`.
`KI + AgNO_3 to AgI + KNO_3`
Millimoles of KI are maximum in option (c).