1. Tardigrade
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  3. Chemistry
  4. At 730° C the vapour density of iodine under a pressure of 1 atm is 97.45 % of the theoretical value, on the assumption that the molecule of gaseous iodine is diatomic. What is the degree of dissociation of I 2 ?

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Q. At $730^{\circ} C$ the vapour density of iodine under a pressure of $1$ atm is $97.45 \%$ of the theoretical value, on the assumption that the molecule of gaseous iodine is diatomic. What is the degree of dissociation of $I _{2}$ ?

Equilibrium

Solution:

van't Hoff factor $(i)=\frac{\text { Theoretical value of mol. wt. }}{\text { Observed value of mol. wt. }}$

image

Total number of moles at equilibrium $=1-\alpha+2 \alpha=1+\alpha$

Observed molecular wt. $=\frac{97.45}{100} \times 254=247.52$

$\therefore i=1+\alpha$

$ \Rightarrow \frac{254}{247.52}=1+\alpha$

$247.52 \alpha=254-247.52=6.48 $

$\Rightarrow \alpha=\frac{6.48}{247.52}=0.0262$