The colligative properties of electrolytes require a slightly dif… - Vidyadip

Question

The colligative properties of electrolytes require a slightly different approach than the one used for the colligative properties of non-electrolytes. The electrolytes dissociate into ions in solution. It is the number of solute particles that determines the colligative properties of a solution. The electron solutions, therefore, show abnormal colligative properties. To account for this effect we define a quantity called the van't Hoft factor, given
by
$i=\frac{\text { Actual number of particles in solution a fter dissociation }}{\text { Number of formula units initially dissolved in solution }}$
$i=1 ($ for non$-$electrolytes$)$
$i>1 ($ for electrolytes, undergoing dissociation$)$
$i<1 ($ for solutes, undergoing association $).$
$i.0.1 M K _4\left[ Fe ( CN )_6\right]$ is $60 \%$ ionized. What will be its van't Hoff factor?
$ii.$ When a solution of benzoic acid dissolved in benzene such that it undergoes in molecular association and its molar mass approaches $244.$ In which form Benzoic molecules will exist?
$iii.$ How does van't Hoff factor $i$ and degree of association a are related if benzoic acid undergoes dimerisation in benzene solution? $\left( i =1 \frac{-\alpha}{2}\right.$ or $\left.i =1+\alpha\right)(2)$
OR
$iii.$ What do you mean by colligative properties of solutions?

✓

Answer

$i.$ We know, $x=\frac{i-1}{n-1}$
Where, $n =5$ and $x =0.6\left(\because 60 \%=\frac{60}{100}=0.6\right.$ ionized $)$
So, $0.6=\frac{i-1}{5-1}$
$0.6 \times 4= i -1$
$2.4= i -1$
$2.4+1= i$
$i=3.4$
$ii.$ Benzoic molecules exist as a dimer.
$iii. i=1 \frac{-\alpha}{2}$

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