💏intro to chemistry review

key term - Ebullioscopy

Definition

Ebullioscopy is a colligative property that measures the boiling point elevation of a solution compared to the pure solvent. It is a technique used to determine the molecular mass of a solute by observing the increase in the boiling point of the solution.

5 Must Know Facts For Your Next Test

  1. The boiling point elevation is directly proportional to the molal concentration of the solute in the solution.
  2. Ebullioscopy can be used to determine the molecular mass of a non-volatile solute by measuring the boiling point elevation.
  3. The boiling point elevation is a colligative property because it depends on the concentration of solute particles, not their identity.
  4. The magnitude of the boiling point elevation is dependent on the van 't Hoff factor, which represents the number of particles produced by the solute.
  5. Ebullioscopy is a useful technique for determining the purity and composition of solutions.

Review Questions

  • Explain how the boiling point elevation of a solution is related to the concentration of the solute.
    • The boiling point elevation of a solution is directly proportional to the molal concentration of the solute. As the concentration of the non-volatile solute increases, the boiling point of the solution increases compared to the pure solvent. This is because the presence of the solute particles lowers the vapor pressure of the solution, requiring a higher temperature to reach the boiling point.
  • Describe how ebullioscopy can be used to determine the molecular mass of a solute.
    • Ebullioscopy can be used to determine the molecular mass of a non-volatile solute by measuring the boiling point elevation of the solution. The magnitude of the boiling point elevation is directly related to the molal concentration of the solute, which is inversely proportional to the molecular mass. By measuring the boiling point elevation and knowing the molal concentration of the solution, the molecular mass of the solute can be calculated using the ebullioscopic constant, a colligative property specific to the solvent.
  • Analyze the role of the van 't Hoff factor in the ebullioscopic determination of molecular mass.
    • The van 't Hoff factor, 'i', represents the number of particles produced by the dissociation or association of the solute in the solution. This factor is crucial in the ebullioscopic determination of molecular mass because it affects the magnitude of the boiling point elevation. A higher van 't Hoff factor, indicating greater particle formation, will result in a larger boiling point elevation for a given solute concentration. By incorporating the van 't Hoff factor into the ebullioscopic equation, the molecular mass of the solute can be accurately determined, even for solutes that undergo partial dissociation or association in the solution.

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