Question

The van't Hoff factor for a dilute solution of $K_3\left[Fe{\left(CN\right)}_6\right]$ is likely to be:

• A. $10$
• B. $4$
• C. $\frac{1}{4}$
• D. $5$

Answer 1

The correct option is B $4$

$K_3\left[Fe{\left(CN\right)}_6\right]$ is a quaternary electrolyte as $A_{3}B$

$K_3\left[Fe{\left(CN\right)}_6\right]\rightleftharpoons 3K^{+}+{\left[Fe{CN}_6\right]}^{3-}$

$1$ $0$ $0$
$(1-x)$ $3x$ $x$

Van't Hoff factor $\left(i\right)=[1+(y-1\left)x\right]$

$i=[1+(4-1\left)x\right]$

$i=1+3x$

If it completely dissociates, then $x=1$

$\therefore$ van't Hoff factor $\left(i\right)=4$