A solution is made by dissolving 100 g of essentially nonvolatile ethylene glycol (C₂H₆O₂) in
500 g of water. What is the resulting freezing point of the solution (K_f = 1.86°C/m) ?

Question

Quizplus · Accepted Answer

The freezing point depression is given by the equation:ΔT_f = K_f * mwhere ΔT_f is the change in freezing point, K_f is the freezing point depression constant for the solvent, and m is the molality of the solution.The molality of the solution is given by:m = moles of solute / kilograms of solventThe moles of solute is given by:moles of solute = mass of solute / molar mass of soluteThe mass of solute is 100 g, and the molar mass of ethylene glycol is 62.07 g/mol. Therefore, the moles of solute is:moles of solute = 100 g / 62.07 g/mol = 1.61 molThe kilograms of solvent is given by:kilograms of solvent = mass of solvent / 1000 g/kgThe mass of solvent is 500 g. Therefore, the kilograms of solvent is:kilograms of solvent = 500 g / 1000 g/kg = 0.5 kgTherefore, the molality of the solution is:m = 1.61 mol / 0.5 kg = 3.22 mol/kgThe freezing point depression constant for water is 1.86°C/m. Therefore, the freezing point depression is:ΔT_f = 1.86°C/m * 3.22 mol/kg = -5.99°CThe freezing point of the solution is:freezing point = 0°C - ΔT_f = 0°C - 5.99°C = -5.99°CTherefore, the correct answer is A.

A Solution Is Made by Dissolving 100 G of Essentially