Question

Which of the following dilute solutions have vant hoff factor equal to 4?
(Assume complete ionisation)

• A. $N{a}_{2}S{O}_4$
• B. $Ca{F}_2$
• C. $K_{3}P{O}_4$
• D. $(N{H}_4{)}_{2}C{O}_3$

Answer 1

The correct option is C $K_{3}P{O}_4$

$\text{van't Hoff factor}\left(i\right)=\frac{\text{Number of molecules (actual)}}{\text{Number of molecules (expected)}}$
Option (a) :
$N{a}_{2}S{O}_4\to 2N{a}^{+}\left(aq\right)+S{O}_4^{2-}\left(aq\right)$
$i=3$

Option (b):
$Ca{F}_2\to C{a}^{2+}\left(aq\right)+2F^{-}(aq.)i=3$

Option (c)
$K_{3}P{O}_4\to 3K^{+}+P{O}_4^{3-}$
$i=4$

Option (d)
$(N{H}_4{)}_{2}C{O}_3\to 2N{H}_4^{+}+C{O}_3^{2-}$
$i=3$