General chemistryLesson 1 of 1 in the course Solutions and Colloids

Colligative Properties: Concentrations, Phase Changes, Osmosis, and Electrolytes

5 flashcards · 5 quiz questions · 5 match pairs · 4 fill-in sentences · English

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Summary

This lesson introduces concentration units that are especially useful for describing colligative properties. Unlike molarity, mole fraction and molality are based on amounts of matter and do not change when temperature changes the solution’s volume.

A solution’s properties can depend on the identity of its components, but colligative properties depend on the total concentration of dissolved particles. Concentration must therefore be expressed appropriately for the calculation.

All flashcards

What is a colligative property?
A solution property that depends on the concentration of dissolved particles rather than their chemical identities.
What does Raoult’s law relate for a component in an ideal solution?
Its partial vapor pressure to its liquid mole fraction and pure-component vapor pressure: Pi=XiPi∗P_i=X_iP_i^*.
What does the van’t Hoff factor measure?
The ratio of dissolved solute particles to solute formula units.
What is osmotic pressure?
The pressure required to stop net solvent movement through a semipermeable membrane.
What happens during fractional distillation?
Repeated vaporization and condensation separate mixture components along a fractionating column.

Quiz questions

  1. Why can a solution’s molarity change when its temperature changes, even if its component amounts stay fixed?Answer: Its volume can expand or contract with temperature.
  2. For component AA in an ideal solution, which equation gives its partial vapor pressure?Answer: PA=XAPA∗P_A=X_AP_A^*
  3. For an ideal dilute solution containing a nonelectrolyte, how is boiling-point elevation calculated?Answer: ΔTb=Kbm\Delta T_b=K_bm
  4. What can happen to cells placed in a hypotonic solution?Answer: Water can enter the cells, causing them to swell or rupture.
  5. Why are measured van’t Hoff factors for strong electrolytes often below ideal predictions?Answer: Interionic attractions can reduce the number of independently behaving particles.

Based on Chemistry 2e by Paul Flowers, Klaus Theopold, Richard Langley, William R. Robinson, PhD (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.

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