1. Tardigrade
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  3. Chemistry
  4. The freezing point of benzene decreases by 0.45° C when 0.2 g of acetic acid is added to 20 g of benzene. If acetic acid associates to form a dimer in benzene, percentage association of acetic acid in benzene will be: K f for benzene =5.12 K kg .mol -1)

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Q. The freezing point of benzene decreases by $0.45^{\circ} C$ when $0.2 \,g$ of acetic acid is added to $20\, g$ of benzene. If acetic acid associates to form a dimer in benzene, percentage association of acetic acid in benzene will be: $K _{ f }$ for benzene $=5.12 \,K\, kg \,\left.mol ^{-1}\right)$

NTA AbhyasNTA Abhyas 2022

Solution:

$\Delta T_{f}=i\times m\times k_{f}$
$0.45=i\times \frac{0 . 2 \times 1000}{60 \times 20}\times 5.12$
$i=0.527=1-\alpha +\frac{\alpha }{n}$ for association
$0.527=1-\alpha +\frac{\alpha }{2}=1-\frac{\alpha }{2}$
$\frac{\alpha }{2}=1-0.527=0.473\alpha =0.946\%\alpha =94.6$