Question

What is correct sequence of the increasing coagulation value of the following electrolyte for the coagulation of $Fe(OH{)}_3$ solution?
$\left(i\right)N{a}_{3}P{O}_4,\left(ii\right)KCl,\left(iii\right)K_{2}S{O}_4,\left(iv\right)K_4\left[Fe\right(CN{)}_6]$

• A. $iv>i>iii>ii$
• B. $ii>iii>i>iv$
• C. $i>ii>iii>iv$
• D. $iv>iii>ii>i$

Answer 1

The correct option is A $iv>i>iii>ii$

According to Hardy- Schulze rule, greater the valence of the flocculating ion, more is the coagulation.
The cation is same in the given compounds and the anions are $P{O}_4^{3-},C{l}^{-},S{O}_4^{2-},\left[Fe\right(CN{)}_6{]}^{4-}$.
So, increasing coagulation value is $K_4\left[Fe\right(CN{)}_6]>K_{3}P{O}_4>K_{2}S{O}_4>KCl$.