Calculate the cryoscopic constant when 0.8 gram nonvolatile solute with molar mass $64 \mathrm{~g}…

Calculate the cryoscopic constant when 0.8 gram nonvolatile solute with molar mass $64 \mathrm{~g} \mathrm{~mol}^{-1}$ dissolved in 43 gram solvent lowers the freezing point by $0.34 \mathrm{~K}$.
  1. $2.5 \mathrm{~K} \mathrm{~kg} \mathrm{~mol}^{-1}$
  2. $2.0 \mathrm{~K} \mathrm{~kg} \mathrm{~mol}^{-1}$
  3. $0.85 \mathrm{~K} \mathrm{~kg} \mathrm{~mol}^{-1}$
  4. $1.17 \mathrm{~K} \mathrm{~kg} \mathrm{~mol}^{-1}$

Solution

$\begin{aligned} & \Delta \mathrm{T}_{\mathrm{f}}=\mathrm{k}_{\mathrm{f}} \mathrm{m} \\ & 0.34=\mathrm{k}_{\mathrm{f}} \times \frac{0.8}{64} \times \frac{1000}{43} \\ & \mathrm{k}_{\mathrm{f}}=1.169 \sim 1.17\end{aligned}$

Asked in: MHT CET 2022 (10 Aug Shift 1)

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