Question

Which one of the following electrolytes has the same value of van’t Hoff’s factor $\left(i\right)$ as that of $A{l}_2(S{O}_4{)}_3$
(if all are $100\%$ ionised) ?

[AIPMT 2015]

• A. $K_4\left[Fe\right(CN{)}_6]$
• B. $K_3\left[Fe\right(CN{)}_6]$
• C. $K_{2}S{O}_4$
• D. $Al(N{O}_3{)}_3$

Answer 1

The correct option is A $K_4\left[Fe\right(CN{)}_6]$

van't Hoff factor
$A{l}_2(S{O}_4{)}_3\to 2A{l}^{+3}+3S{O}_4^{2-}$
$i=5$

option (a);
$K_3\left[Fe\right(CN{)}_6]\to 3K^{+}+[Fe(CN{)}_6{]}^{3-}$
$i=4$

option (b);
$K_4\left[Fe\right(CN{)}_6]\to 4K^{+}+[Fe(CN{)}_6{]}^{4-}$
$i=5$

option (c):
$Al(N{O}_3{)}_3\to A{l}^{3+}+3N{O}_3^{-}$
$i=4$

Option (d):
$K_{2}S{O}_4\to 2K^{+}+S{O}_4^{2-}$
$i=3$

Hence, Option (b) is correct