Calculate molar mass of nonvolatile solute if a solution containing 0.35 g solute in 100 g .water has…

Calculate molar mass of nonvolatile solute if a solution containing 0.35 g solute in 100 g .water has boiling point elevation 0.01 K $\left[\mathrm{K}_{\mathrm{b}}=0.50 \mathrm{~K} \mathrm{~kg} \mathrm{~mol}^{-1}\right.$ ]
  1. $265 \mathrm{~g} \mathrm{~mol}^{-1}$
  2. $175 \mathrm{~g} \mathrm{~mol}^{-1}$
  3. $105 \mathrm{~g} \mathrm{~mol}^{-1}$
  4. $195 \mathrm{~g} \mathrm{~mol}^{-1}$

Solution

$\begin{aligned} & \Delta \mathrm{T}_{\mathrm{b}}=\mathrm{K}_{\mathrm{b}} \mathrm{m}=\mathrm{K}_{\mathrm{b}} \frac{1000 \mathrm{~W}_2}{\mathrm{~W}_1 \mathrm{M}_2} \\ & \mathrm{M}_2=\frac{1000 \times 0.50 \mathrm{~K} \mathrm{~kg} \mathrm{~mol}^{-1} \times 0.35 \mathrm{~g}}{100 \mathrm{~g} \times 0.01 \mathrm{~K}} \\ & \mathrm{M}_1=175 \mathrm{~g} \mathrm{~mol}^{-1}\end{aligned}$

Asked in: MHT CET 2024 (10 May Shift 2)

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