Lec 17 | MIT 5.112 Principles of Chemical Science, Fall 2005

TL;DR

This lecture discusses the concepts of intermolecular interactions, specifically dispersion interactions, dipole-dipole interactions, and hydrogen bonding, and their influence on chemical reactions and thermodynamics.

Transcript

The following content is provided by MIT OpenCourseWare under a Creative Commons license. Additional information about our license and MIT OpenCourseWare in general is available at ocw.mit.edu. -- sometimes called the van der Waal's interactions. And we saw that we could make a molecule between two inert gas atoms, like argon two or xenon two, by ... Read More

Key Insights

• 🖐️ Intermolecular interactions, such as dispersion interactions and dipole-dipole interactions, play a crucial role in determining the stability and behavior of molecules.
• 🧑‍🏭 The strength of intermolecular interactions is influenced by factors such as polarizability, dipole moment, and shape.
• 🥵 The enthalpy of a chemical reaction can be calculated by considering the bond enthalpies of the reactants and products, or by using heats of formation from the elements involved.

Questions & Answers

Q: What determines the strength of dispersion interactions?

The strength of dispersion interactions is determined by the polarizability of the atoms or molecules involved. The polarizability increases with the number of electrons present.

Q: How does increasing the temperature affect intermolecular interactions?

Increasing the temperature leads to weaker intermolecular interactions as the molecules gain more kinetic energy and can overcome attractive forces. This can result in the gas phase behavior of molecules.

Q: What is the role of shape in determining intermolecular interactions?

The shape of molecules is important in determining intermolecular interactions. Different shapes can affect the distance between dipoles, leading to variations in the strength of attractive interactions.

Q: How does hydrogen bonding differ from other types of intermolecular interactions?

Hydrogen bonding occurs specifically between a hydrogen atom bonded to an electronegative atom and another molecule. It is generally stronger than dispersion and dipole-dipole interactions and plays a significant role in the properties of substances such as water and biological molecules.

Summary & Key Takeaways

• The lecture introduces the concept of intermolecular interactions, focusing on dispersion interactions, dipole-dipole interactions, and hydrogen bonding.

• The strength of these interactions and the resulting stability of molecules are determined by factors such as polarizability and dipole moment.

• The lecture also discusses the role of intermolecular interactions in determining the boiling points of substances and the behavior of molecules at different temperatures.