An ethylene glycol solution contains 21.2 g of ethylene glycol (C2H6O2) in 85.4 mL of water. Determine the freezing point and boiling point of the solution. (Assume a density of 1.00 g/mL for water.)

Name: Chemistry: A Molecular Approach
Author: Tro
ISBN: 9780134112831

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Calculate the molality of the solution by first determining the moles of ethylene glycol (C_2H_6O_2) using its molar mass.

Convert the volume of water to mass using the given density (1.00 g/mL), then use this mass to calculate the molality of the solution.

Use the freezing point depression formula, \( \Delta T_f = i \cdot K_f \cdot m \), where \( i \) is the van't Hoff factor (1 for ethylene glycol), \( K_f \) is the freezing point depression constant for water, and \( m \) is the molality.

Calculate the new freezing point by subtracting \( \Delta T_f \) from the normal freezing point of water (0°C).

Use the boiling point elevation formula, \( \Delta T_b = i \cdot K_b \cdot m \), where \( K_b \) is the boiling point elevation constant for water, to find the change in boiling point, and add \( \Delta T_b \) to the normal boiling point of water (100°C).

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Colligative Properties

Colligative properties are physical properties of solutions that depend on the number of solute particles in a given amount of solvent, rather than the identity of the solute. These properties include boiling point elevation and freezing point depression, which are crucial for determining how the presence of a solute like ethylene glycol affects the freezing and boiling points of water.

Freezing Point Depression

Freezing point depression is a colligative property that describes the lowering of the freezing point of a solvent when a solute is added. The extent of this depression can be calculated using the formula ΔTf = i * Kf * m, where ΔTf is the change in freezing point, Kf is the freezing point depression constant of the solvent, and m is the molality of the solution.

Boiling Point Elevation

Boiling point elevation is another colligative property that indicates the increase in the boiling point of a solvent when a solute is dissolved in it. This can be calculated using the formula ΔTb = i * Kb * m, where ΔTb is the change in boiling point, Kb is the boiling point elevation constant of the solvent, and m is the molality of the solution. Understanding this concept is essential for determining how the boiling point of water changes in the presence of ethylene glycol.