1. Tardigrade
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  3. Chemistry
  4. When 20 g of naphthoic acid (C11H8O2) is dissolved in 50 g of benzene (Kf = 1.72 K kg mol-1), a freezing point depression of 2 K is observed. The van-t Hoff factor (i) is

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Q. When $20\, g$ of naphthoic acid ($C_{11}H_8O_2$) is dissolved in $50 \,g$ of benzene ($K_f = 1.72 \,K \,kg \,mol^{-1}$), a freezing point depression of $2 \,K$ is observed. The van-t Hoff factor (i) is

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Solution:

Molality$=\bigg(\frac{20}{172}\bigg) \times \frac{1000}{50} =2.325\, m$
$\Rightarrow -\Delta T_f =2 = iK_f.m$
$\Rightarrow i=\frac{2}{1.72 \times 2.325}=0.5$