Which mixture of the solution will lead to the formation of negatively charged colloidal [AgI] I- sol. ?
- 50 mL of 2 M AgNO3 + 50 mL of 1.5 M KI
- 50 mL of 0.1 M AgNO3 + 50 mL of 0.1 M KI
- 50 mL of 1 M AgNO3 + 50 mL of 1.5 M KI
- 50 mL of 1 M AgNO3 + 50 mL of 2 M KI
Answer
(3) 50 mL of 1 M AgNO3 + 50 mL of 1.5 M KI, (4) 50 mL of 1 M AgNO3 + 50 mL of 2 M KI
Solution
As per NCERT, when AgNO3 solution is added to excess KI solution, the precipitated AgI adsorbs I- ions and a negatively charged sol AgI/I- is formed. So KI must be in excess.
Millimoles = molarity volume (mL):
(1) AgNO3 = 2 50 = 100; KI = 1.5 50 = 75 Ag+ in excess, positive sol AgI/Ag+
(2) AgNO3 = 0.1 50 = 5; KI = 0.1 50 = 5 no excess ion, no charged sol
(3) AgNO3 = 1 50 = 50; KI = 1.5 50 = 75 I- in excess, negative sol
(4) AgNO3 = 1 50 = 50; KI = 2 50 = 100 I- in excess, negative sol
Mixtures (3) and (4) give the negatively charged [AgI] I- sol.
Answer: (3), (4)