Interactive Self-Study Module: Enthalpy of Mixing and Deviation from Raoult's Law

Overview:

This module uses screencasts and an interactive simulation to explain the change in energy associated with mixing liquids, and the relationship between heat of mixing and deviations from Raoult’s law. It then provides a quiz simulation and example problems to allow users to test themselves. Your retention of material in this module will increase if you write down reasons for your answers to ConcepTests, questions in screencasts, and questions to answer before using the interactive simulation, and you try to solve the example problems before watching the screencast solutions. We suggest using the learning resources in the following order:

  1. Attempt to answer the multiple-choice ConcepTest and solve the example problem before watching the screencasts or working with the simulations.
  2. Watch the screencasts that describe enthalpy changes when liquids mix and answer the questions within the screencasts.
  3. Review important equations for this topic.
  4. Use the interactive simulation to further understand the behavior of energy changes when forming nonideal solutions.
  5. Use the quiz simulation to better understand the enthalpies and entropies of mixing.
  6. Try to solve the example problems before watching the solutions in the screencasts.
  7. Answer the ConcepTests.
  8. Look at the list of key points, but only after you try to list the key points yourself.
Motivation:
  • For nonideal mixtures, the enthalpy change on mixing can be positive or negative. Such mixtures exhibit vapor-liquid equilibrium behavior that deviates from Raoult’s law. 
  • This module is intended for a thermodynamics course.
Before studying this module, you should be able to:
After studying this module, you should be able to:
  • Calculate the heat of mixing from an enthalpy versus mole fraction diagram when two pure components are mixed.
  • Calculate the adiabatic temperature from an enthalpy versus mole fraction diagram when two pure components are mixed.
  • Calculate the adiabatic temperature from an enthalpy-mole fraction diagram when two mixtures of different mole fractions (but containing the same two components) are mixed.
  • Determine from an enthalpy-mole fraction diagram whether mixing of two pure components is endothermic, exothermic, or ideal.
  • Predict positive or negative deviations from Raoult’s law from the heat of mixing and predict whether mixing is endothermic or exothermic from deviations from Raoult’s law.