A solution of nonvolatile solute is obtained by dissolving $3.5 \mathrm{~g}$ in $100 \mathrm{~g}$ solvent…

A solution of nonvolatile solute is obtained by dissolving $3.5 \mathrm{~g}$ in $100 \mathrm{~g}$ solvent has boiling point elevation $0.35 \mathrm{~K}$. Calculate the molar mass of solute. $\left(\right.$ Molal elevation constant $\left.=2.5 \mathrm{~K} \mathrm{~kg} \mathrm{~mol}^{-1}\right)$
  1. $270 \mathrm{~g} \mathrm{~mol}^{-1}$
  2. $260 \mathrm{~g} \mathrm{~mol}^{-1}$
  3. $250 \mathrm{~g} \mathrm{~mol}^{-1}$
  4. $240 \mathrm{~g} \mathrm{~mol}^{-1}$

Solution

$\mathrm{M}_2=\frac{\mathrm{K}_{\mathrm{b}} \times \mathrm{W}_2 \times 1000}{\Delta \mathrm{T}_{\mathrm{b}} \times \mathrm{W}_1}=\frac{2.5 \times 3.5 \times 1000}{0.35 \times 100}=250 \mathrm{~g} \mathrm{~mol}^{-1}$

Asked in: MHT CET 2023 (09 May Shift 1)

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