The figure at right shows cation surface excess $($q$)$ on an adsorbent as a function of $pH.$ The PZNPC of the absorbent is $pH6$

$($a$)$ What accounts for the increase in $q$ with increasing $pH?3$ pts

$($b$)$ Assuming that the line shown here refers to an ion that adsorbs to the surface by electrostatic attraction only $($outer$-$sphere or diffuse ion swarm$),$ plot another line on the same plot showing higher affinity adsorption, in this case, for an ion that adsorbs via innersphere complex formation. Explain why you plotted the line where you did. $7$ pts

$($c$)$ Finally, plot and label on the same graph, two more lines, this time for anion adsorption as a function of $pH$ that reflects:

$($i$)$ high affinity adsorption $2$ pts and

$($ii$)$ low affinity adsorption. $2$ pts