Chapter 23, Problem 23.15P

(a)

Interpretation Introduction

Interpretation:

Electro-osmosis process has to be explained.

Concept Introduction:

Electro-osmosis is a kinetic process in which the transport of bulk fluid through a porous membrane under the influence of an electric field is taken place.

(b)

Interpretation Introduction

Interpretation:

Reason behind electro-osmotic flow in a silica capillary to be five times faster at $\text{pH}$ 9 than in $\text{pH}$ 3 has to be explained.

Concept Introduction:

Electro-osmotic velocity is the speed of the dominant ion in the diffused part of the double layer. It is calculated as follows:

    ${\text{U}}_{\text{Electro-osmosis}}=\left({\text{μ}}_{\text{Electro-osmosis}}\right)\left(\text{E}\right)$

Here, ${\text{U}}_{\text{Electro-osmosis}}$ is speed of the flow of electro-osmosis.

${\text{μ}}_{\text{Electro-osmosis}}$ is ionic mobility of the dominant ion.

$\text{E}$ is electrode potential between cathode and anode plate.

(c)

Interpretation Introduction

Interpretation:

Reason behind small flow and $\text{pH}$ to be nearly independent when $\text{Si}-\text{OH}$ group on a silica capillary wall are converted into ${\text{Si-O-(CH}}_{\text{2}}{\text{)}}_{\text{17}}{\text{CH}}_{\text{3}}$ has to be explained.

Concept Introduction:

Refer to part (b).