Introduction to Chemistry 6 - Non-covalent Interactions PDF
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Dr Thomas Höfken
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Summary
This document provides a summary of non-covalent interactions, a topic within introduction to chemistry. It explains various forces like dispersion forces, dipole-dipole interactions, and hydrogen bonds, along with their influence on physical properties like solubility and melting/boiling points.
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Introduction to chemistry 6 Non-covalent interactions Dr Thomas Höfken Non-covalent interactions - Much weaker than covalent bonds - Important intermolecular forces - Determine physical properties - solubility - melting point -… Types of non-covalent interactions -...
Introduction to chemistry 6 Non-covalent interactions Dr Thomas Höfken Non-covalent interactions - Much weaker than covalent bonds - Important intermolecular forces - Determine physical properties - solubility - melting point -… Types of non-covalent interactions - Dispersion forces - Permanent dipolar interactions - Hydrogen bonds - Ionic interactions - Hydrophobic forces Dispersion forces in unpolar molecules H―H - Short- lived - Very weak Dispersion forces in unpolar molecules Permanent dipoles + - Polar covalent bonds + - + - + - van der Waals forces - Dipole-dipole interactions - Dispersion forces Hydrogen bonds - Between hydrogen bound to an electronegative atom and an electronegative atom - Electronegative elements: Oxygen, nitrogen - + + Hydrogen bonds in ice Ionic interactions Hydrophobic forces Driven by a molecule’s behaviour when exposed to water - Polar molecules are hydrophilic (water-soluble) - Unpolar molecules are hydrophobic (water-insoluble) Solubility - the maximum amount of solute that dissolves in a given amount of solvent at a specific temperature -“Like dissolves like” - Polar molecules are most soluble in polar solvents - Nonpolar molecules are most soluble in nonpolar solvents Interaction of water and ammonia - - + + + + + Solutions of ionic and covalent compounds - Ionic compounds often dissolve in water, where they dissociate - form positive and negative ions in solution - Electrolytes: ions present in solution allowing the solution to conduct electricity States of matter Solid Liquid Gas Many non- Fewer non- Virtually no non- covalent covalent covalent interactions interactions interactions Melting and boiling points - Energy is used to overcome the intermolecular attractive forces in a substance, driving the molecules into a less associated phase - The greater the intermolecular force, the more energy is required leading to - Higher melting point of a solid - Higher boiling point of a liquid Boiling point: -161C 100C
