Solutions and Colligative Properties - Result Question 8-1
8. $\mathrm{K}_2 \mathrm{HgI}_4$ is $40 %$ ionised in aqueous solution. The value of its van’t Hoff factor $(i)$ is
(2019 Main, 11 Jan II)
(a) $1.6$
(b) $1.8$
(c) $2.2$
(d) $2.0$
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Answer:
Correct Answer: 8. (b)
Solution:
The ionisation of $\mathrm{K}_2 \mathrm{HgI}_4$ in aqueous solution is as follows:
$ \mathrm{K}_2\left[\mathrm{HgI}_4\right] \rightleftharpoons 2 \mathrm{~K}^{+}+\left[\mathrm{HgI}_4\right]^{2-} $
van’t Hoff factor (i) for ionisation reaction is given as, $i=1+\alpha(n-1)$
where,
$n=$ number of ions,
$\alpha=$ degree of ionisation or dissociation
From above equation, it is clear that $n=3$
$i =1+0.4(3-1) $ $ \text { [Given, } % \alpha=40 % \text { or } \alpha=0.4 \text { ] }$
$=1.8 $
BETA
