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Solution: 1) The equation to use is this: Δt = i K b m. 2) Look up necessary values: boiling point of pure benzene: 80.1 °C ebullioscopic constant for benzene: 2.53 °C/m. 3) Insert values into equation: 1.1 °C = (1) (2.53 °C/m) (x / 0.200 kg) x = 0.0869565 mol. Remember that molality is moles solute / kilograms solvent.
Boiling point elevation is the difference in temperature between the boiling point of the pure solvent and that of the solution. The molal boiling-point elevation constant is equal to the change in the boiling point for a 1-molal solution of a nonvolatile molecular solute.
Example #1: What is the boiling point elevation when 11.4 g of ammonia (NH 3) is dissolved in 200. g of water? K b for water is 0.52 °C/m. Solution. 1) Determine molality of 11.4 g of ammonia in 200. g of water: 11.4 g / 17.031 g/mol = 0.6693676 mol. 0.6693676 mol / 0.200 kg = 3.3468 m. 2) Determine bp elevation: Δt = i K b m.
Learning Objectives. By the end of this section, you will be able to: Express concentrations of solution components using mole fraction and molality. Describe the effect of solute concentration on various solution properties (vapor pressure, boiling point, freezing point, and osmotic pressure)
The colligative properties of a solution depend on the relative numbers (concentration) of solute and solvent particles, they do not depend on the nature of the particles. Colligative properties change in proportion to the concentration of the solute particles. We distinguish between four colligative properties: vapor pressure lowering,
Determine the boiling point of a solution that contains 78.8 g of naphthalene (C 10 H 8, molar mass = 128.16 g/mol) dissolved in 722 mL of benzene (d = 0.877 g/ml). Pure benzene has a boiling point of 80.1°C and a boiling point elevation constant of 2.53°C/m.
23 Ιουλ 2021 · The formula for the change in the boiling point of a solution, therefore, contains a proportionality constant, abbreviated K b, which is a property determined experimentally and must be read from a table such as the one below.
