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What mass of ...

Question

What mass of an organic compound $(M w_{0} = 156)$ must be dissolved in 50 mL of an organic solvent $(d = 0.9 g {c c}^{- 1})$ water to lower the freezing point by ${0.48}^{o} C$ . $K_{f}$ of benzene =5.12.

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Solution

$Δ T_{f} = \frac{K_{f} \times W_{2} \times 1000}{M w_{2} \times W_{1}}$
$W_{1} = 50 \times 0.9$
$0.48 = \frac{5.12 \times W_{2} \times 1000}{156 \times 50 \times 0.9}$
$W_{2} = 0.658 g$

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