# Question 3481a

Mar 25, 2016

See below.

#### Explanation:

Structure of Micelles

The AgI micelle is formed by the reaction

${\text{AgNO"_3 + "KI" → "AgI" + "KNO}}_{3}$

The micelle core consists of many solid particles.

We can write this as:

$\underbrace{m \text{AgI")_color(red)("core}}$

With a surplus of ${\text{AgNO}}_{3}$, there will be next to the core a layer of preferentially adsorbed ${\text{Ag}}^{+}$ ions.

We can write this as:

underbrace( m "AgI")_color(red)("core")color(white)(l) n "Ag"^+, where $n$ is the number of ions.

The particle is now positively charged and attracts $\text{NO"_3^"-}$ ions from solution.

We now have an adsorption layer of oppositely charged counterions surrounding the core:

[underbrace(underbrace( m "AgI")_color(red)("core")color(white)(l)overbrace(n "Ag"^+ (n-x) "NO"_3^"-")^(color(brown)("adsorption layer")))_color(red)("granule")]^(x+)

The core, along with the adsorption layer, is called a granule.

The granule has a positive charge and is surrounded by a diffusion layer of $\text{NO"_3^"-}$ counterions.

underbrace([underbrace(underbrace( m "AgI")_color(red)("core")color(white)(l)overbrace(n "Ag"^+ (n-x) "NO"_3^"-")^(color(brown)("adsorption layer")))_color(red)("granule")]^(x+) overbrace(x color(white)(l)"NO"_3^"-")^(color(brown)("diffusion layer")))_color(blue)("micelle")#

The complete assembly is called a micelle.

Factors affecting stability of $\text{AgI}$ micelles

(a) Double layer overlap

Colloids with a double layer at their surfaces are stable due to repulsions caused by interpenetration of the diffuse parts of the double layers. 