How many moles of the nonelectrolyte, propylene glycol (C₃H₈O₂)should be dissolved in 800.0 g of water to prepare a solution whose freezing point is -3.72°C?For water, K_f is 1.86°C m^-1 and K_b is 0.512°C m^-1.

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Quizplus · Accepted Answer

The freezing point depression formula is ΔTf = i * Kf * m. Since propylene glycol is a nonelectrolyte, i = 1. ΔTf = 0°C - (-3.72°C) = 3.72°C. Rearranging the formula gives m = ΔTf / Kf = 3.72°C / 1.86°C m^-1 = 2.00 m. Since m = moles of solute / kg of solvent, moles of solute = m * kg of solvent = 2.00 m * 0.800 kg = 1.60 moles.

How Many Moles of the Nonelectrolyte, Propylene Glycol (C3H8O2)should Be

How Many Moles of the Nonelectrolyte, Propylene Glycol (C₃H₈O₂)should Be