Respuesta :

Edufirst

Answer:

  • 2 moles of glucose would be needed to lower the freezing point of one kg of water 3.72ºC.

Explanation:

Lowering the freezing point of a solvent, when a nonvolatils solute is added, is a colligative property that follows the equation:

        [tex]\Delta T_f=m\times k_f\times i[/tex]

Where:

  • ΔTf is the depression on the freezing point
  • Kf is the molal kryoscopic constant of the solvent. For water it is 1.86 ºC/m
  • i is the van't Hoff factor. For molecular compounds, such as glucose, it is 1.

Then, you can calculate the molality of the solution:

  • 3.72ºC = m × 1.86ºC/m × 1

Clear m:

  • m = 3.72ºC / (1.86ºC/m)
  • m = 2 mol of solute /kg of solvent

Since molality is the number of moles per kg of solvent, you would need 2 moles of glucose to lower the freezing point of one kg of water 3.72ºC.

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