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Find the freezing point of the solution containing 3.6 g of glucose dissolved in 50 g of H2O. (Kf for H2O = 1.86 K/m). |
Answer» Mass of glucose, WB = 3.6 g Molecular mass of glucose = 180 g mol-1 Mass of solvent, WA = 50 g Kf for H2O = 1.86 K/m = 1.86 K kg-1 mol-1 MB = \(\frac{1000K_f\,\times\,W_B}{W_A\,\times\,\bigtriangleup T_f}\) ∴ \(\bigtriangleup T_f\) = \(\frac{1000K_f\,\times\,W_B}{W_A\,\times\,M_B}\) = \(\frac{1000\,g\,kg^{-1}\,\times\,1.86\,K\,kg^{-1}\,mol^{-1}\,\times\,3.6\,g}{50\,g\times180\,g\,mol^{-1}}\) = 0.744 K. i.e., ΔTf = T°f – Tf = 0.744 K ∴ Freezing point of the solution, Tf = T°f – ΔT = 273 K – 0.744 K = 272.3 K |
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