# . On adding AgNO3 solution into KI solution a negatively charged colloidal

sol is obtained when they are in

A: 50 mL of 0.1 M AgNO3 + 40 mL of 0.1 M KI

B: 50 mL of 0.1 M AgNO3 + 50 mL of 0.2 M KI

C: 50 mL of 0.2 M AgNO3 + 50 mL of 0.2 M KI

D: None of these

Explanation :

The correct answer is option B.

The basic concept involved is that to form a negatively charged colloid from given solutions,

there should be more KI in comparison to AgNObecause eventually the Ag+ and I- will be involved in Helmholtz double layer formation while other spectator ions will only neutralize them.

Amongst  the given options,KI is in excess in option B which is given as follows:

A. 50 mL of 0.1 M AgNO= 5mmoles AgNO3

40 ml of 0.1 M KI = 4 mmoles of KI

So, AgNO is comparatively more.

B. 50 mL of 0.1 M AgNO= 5mmoles AgNO3

50 ml of 0.2 M KI = 10 mmoles of KI

So, KI is in excess

C. 50 mL of 0.2 M AgNO3  = 10mmoles AgNO3

50 ml of 0.2 M KI = 10 mmoles of KI

Equal amount so precipitation occurs.