Question

In order to coagulate $400\text{ml}$ of $Fe(OH{)}_3$ sol completely, $60\text{ml}$ of $0.1\text{M}$ $KCl$ is required. What will be the coagulation value of $KCl$?

• A. $6$
• B. $10$
• C. $15$
• D. $\frac{1}{15}$

Answer 1

The correct option is C $15$

Coagulation value is the millimoles of an electrolyte that must be added to $1\text{L}$ of a colloidal solution for complete coagulation.
Given,
For $400textmL$ $Fe(OH{)}_3$, millimoles of $KCl$ required $=\text{molarity}\times \text{volume(mL)}=0.1\times 60=6$
Hence,
For $1000\text{mL}$ $Fe(OH{)}_3$, millimoles of $KCl$ required
$=\frac{6}{400}\times 1000=15$
Hence coagulation value of $KCl$ is $15$