Question

Dimerization of benzoic acid occurs in benzene solution, then the relation between van't Hoff factor $i$ and amount of association $x$ is:

• A. $i=(1-x)$
• B. $i=(1+x)$
• C. $i=(1-\frac{x}{2})$
• D. $i=(1+\frac{x}{2})$

Answer 1

Answer: (C)

$i=(1-\frac{x}{2})$

According to Colligatiur property:-

$i=1+(\frac{1}{n}-1)\alpha$

$i\to$ Van't Hoff factor.

$\alpha \to$degree of dissociation/association.

$n\to$ stochiometric co-efficient.

For Benzoic Acid, Dimerisation $n=2$.

$i=1+(\frac{1}{2}-1)\alpha$

$\Rightarrow i=1-\left(\frac{1}{2}\right)\alpha$

$\Rightarrow i=1-\frac{\alpha }{2}$